Liquid ejecting head, liquid ejecting apparatus, and method of controlling liquid ejecting head

Abstract

The invention provides a liquid ejecting head, a liquid ejecting apparatus, and a method of controlling the liquid ejecting head. A liquid ejecting head configured to eject a liquid from an ejection port while moving in a predetermined direction includes: an ejection unit including an ejection element for generating energy for ejecting the liquid from the ejection port; a pressure chamber communicating with the injection port; a separate supply channel for supplying liquid to the pressure chamber; a separate collection channel for collecting liquid from the pressure chamber; and a liquid transport element disposed between the individual supply channel and the individual collection channel, and configured to transport liquid from the individual supply channel to the individual collection channel; and a circulation unit fluidly connected to the ejection unit and configured to circulate the liquid in a common supply channel for collectively supplying the liquid to the plurality of individual supply channels, in which the circulation unit is driven on demand based on a predetermined condition determination.

Description

Technical Field

[0001] This disclosure relates to a liquid jet head, a liquid jetting device including the liquid jet head, and a method for controlling the liquid jet head. Background Technology

[0002] One factor that degrades image quality in existing printheads is the concentration of ink (liquid). In a nozzle that has not been used for printing for a period of time, the ink evaporates, causing it to thicken. When the ink thickens, the print volume and direction may change, resulting in streaks and uneven density in the image, thus degrading image quality.

[0003] U.S. Patent Application Publication No. 2020 / 0238708 (referred to as Document 1) discloses a configuration in which ink is circulated between a liquid ejector head and a body using a body-side pump located outside the liquid ejector head, in addition to a configuration in which ink is circulated by a separate pump arranged in a pressure chamber.

[0004] However, in Reference 1, the frequently driven external pump may cause more evaporation from the nozzle than is required. Summary of the Invention

[0005] In view of the above problems, the purpose of this disclosure is to provide a liquid jet head that can achieve sufficient circulation efficiency while suppressing evaporation from the nozzle.

[0006] The liquid jet head disclosed herein is a liquid jet head configured to eject liquid from a jet nozzle while moving in a predetermined direction, comprising: a jetting unit including: a jetting element configured to generate energy for ejecting liquid from the jet nozzle; a pressure chamber communicating with the jet nozzle; a separate supply channel for supplying liquid to the pressure chamber; a separate collection channel for collecting liquid from the pressure chamber; and a liquid sending element disposed between the separate supply channel and the separate collection channel and configured to transport liquid from the separate supply channel to the separate collection channel; and a circulation unit fluidly connected to the jetting unit and configured to circulate liquid in a common supply channel for centrally supplying liquid to a plurality of the separate supply channels, wherein the circulation unit is driven on demand based on predetermined conditions.

[0007] The features of this disclosure will become apparent from the following description of embodiments with reference to the accompanying drawings. The following description of embodiments is provided by way of example. Attached Figure Description

[0008] Figure 1A and Figure 1B This is a diagram showing a liquid injection device;

[0009] Figure 2 This is an exploded 3D view of the liquid injection head;

[0010] Figure 3A and Figure 3B These are longitudinal cross-sectional views of the liquid injection head and enlarged cross-sectional views of the injection module;

[0011] Figure 4 This is a schematic diagram of the appearance of the loop unit;

[0012] Figure 5 This is a longitudinal cross-sectional view showing the loop path;

[0013] Figure 6 It is a schematic diagram illustrating the loop path;

[0014] Figures 7A to 7C This is a cross-sectional view showing an example of a pressure regulating unit;

[0015] Figure 8A and Figure 8B This is a 3D view of the circulating pump.

[0016] Figure 9 It is along Figure 8A The cross-sectional view of the circulating pump shown is taken along line IX-IX.

[0017] Figures 10A to 10E This is a diagram showing the flow of ink in a liquid jet nozzle;

[0018] Figure 11A and Figure 11B This is a schematic diagram showing the circulation path in the injection unit;

[0019] Figure 12 This is a diagram showing the opening plate 330;

[0020] Figure 13 This is a diagram showing the substrate of the spraying element;

[0021] Figures 14A to 14C This is a cross-sectional view showing the ink flow in the jetting unit;

[0022] Figure 15A and Figure 15B This is a cross-sectional view showing the vicinity of the injection nozzle;

[0023] Figure 16A and Figure 16B This is a cross-sectional view showing a comparative example near the injection nozzle;

[0024] Figure 17 This is a diagram showing a comparative example of a jetting element substrate;

[0025] Figure 18A and Figure 18BThis is a diagram showing the flow channel structure of a liquid injection head;

[0026] Figure 19 This diagram shows the connection between the main body of the liquid injection device and the liquid injection head;

[0027] Figure 20A and Figure 20B This is a diagram showing a portion of the injection module according to the first embodiment;

[0028] Figure 21 This is a diagram illustrating the drive pulses of a liquid transport element;

[0029] Figure 22A and Figure 22B This is a diagram showing a portion of the injection module according to the second embodiment;

[0030] Figure 23A and Figure 23B This is a diagram showing a portion of the injection module according to a third embodiment;

[0031] Figure 24A and Figure 24B This is a diagram showing a portion of the injection module according to the fourth embodiment; and

[0032] Figures 25A to 25C This is a diagram showing a portion of the injection module according to the fifth embodiment. Detailed Implementation

[0033] Embodiments of this disclosure will now be described with reference to the accompanying drawings. These embodiments can be implemented in any configuration, including but not limited to other configurations.

[0034] Preferred embodiments of this disclosure will be described in detail with reference to the accompanying drawings. The following embodiments do not limit the subject matter of this disclosure, and not all combinations of features described in these embodiments are necessarily necessary for the technical solutions of this disclosure. Identical components will be denoted by the same reference numerals. This embodiment will be described using, but not limited to, examples employing a thermal method, in which an electrothermal conversion element generates bubbles to spray the liquid as a spraying element. This disclosure is also applicable to spraying methods using piezoelectric elements (piezoelectric) to spray liquid, or liquid spray heads using other spraying methods. Pumps, pressure regulating units, etc., described below are not limited to the constructions described in the embodiments and drawings. In the following description, the basic structure of this disclosure will first be described, followed by the features of this disclosure.

[0035] <Liquid jetting device>

[0036] Figure 1A and Figure 1BThis is a diagram used to illustrate a liquid injection device, and it is an enlarged view of the liquid injection head and its surroundings. First, refer to... Figure 1A and Figure 1B A schematic construction of the liquid injection device 50 according to this embodiment is described. Figure 1A This is a perspective view schematically showing a liquid jetting device using a liquid jetting head 1. The liquid jetting device 50 according to this embodiment constitutes a serial inkjet printing device, which is configured to print on a printing medium P by jetting ink as a liquid while scanning the liquid jetting head 1.

[0037] The liquid jet head 1 is mounted on a carriage 60. The carriage 60 reciprocates along a guide shaft 51 in the main scanning direction (X direction). Sheet-shaped printing media P is conveyed via transport rollers 55, 56, 57, and 58 in a secondary scanning direction (Y direction) that intersects (orthogonally in this example) the main scanning direction. In the various figures referred to below, the Z direction indicates the vertical direction and intersects (orthogonally in this example) the XY plane defined by the X and Y directions. The liquid jet head 1 is configured to be detachable from and attached to the carriage 60 by a user.

[0038] Liquid injection head 1 includes a circulation unit 54 and an injection unit 3, which will be described later (see [link to documentation]). Figure 2 Although its specific construction will be described later, the injection unit 3 includes multiple injection ports and energy generating elements (hereinafter referred to as injection elements) for generating the injection energy of liquid ejected from each injection port.

[0039] The liquid injection device 50 is also equipped with an ink cartridge 2 as an ink supply source and an external pump 21. The ink stored in the ink cartridge 2 is supplied to the circulation unit 54 via the ink supply pipe 59 by the driving force of the external pump 21.

[0040] The liquid jetting apparatus 50 forms a predetermined image on a printing medium P by repeatedly printing scans. The liquid jetting head 1, mounted on a carriage 60, performs printing by jetting ink while moving along the main scanning direction, and also performs a transport operation to convey the printing medium P along the sub-scanning direction. According to this embodiment, the liquid jetting head 1 can jet four types of ink: black (B), cyan (C), magenta (M), and yellow (Y), and can use these inks to print full-color images. However, the ink that can be jetted from the jetting head 1 is not limited to the above four types. This disclosure also applies to liquid jetting heads used for jetting other types of ink. In short, there is no limitation on the type and quantity of ink to be jetted from the liquid jetting head.

[0041] Furthermore, in the liquid jetting device 50, a cover member (not shown) that covers the surface of the liquid jetting head with the jetting nozzle is disposed at a position separate from the transport path of the printing medium P in the X direction. The cover member covers the surface of the jetting nozzle of the liquid jetting head 1 during non-printing operations and is used to prevent the jetting nozzle from drying out, protect the jetting nozzle, and perform ink suction operations from the jetting nozzle.

[0042] Notice, Figure 1A The liquid ejector head 1 shown represents an example of four circulation units 54 corresponding to four types of ink included in the liquid ejector head 1; however, it is sufficient that the included circulation units 54 correspond to the type of liquid to be ejected. Furthermore, multiple circulation units 54 can be included for the same type of ink. In summary, the liquid ejector head 1 can have a configuration including one or more circulation units. The liquid ejector head 1 can be configured to circulate only at least one type of ink, rather than all four types.

[0043] Figure 1B This is a block diagram showing the control system of the liquid jetting device 50. The CPU 103 serves as a control unit configured to control the operation of various units of the liquid jetting device 50 based on a program such as a processing procedure stored in ROM 101. RAM 102 serves as a workspace for the CPU 103 to perform processing, etc. The CPU 103 receives image data from a host device 400 external to the liquid jetting device 50 and controls the head driver 1A to control the driving of the jetting element 15 and the liquid transport element 1001 disposed in the jetting unit 3. The CPU 103 also controls various drivers disposed in the liquid jetting device. For example, the CPU 103 controls the motor driver 105A of the carriage motor 105 to move the carriage 60, controls the motor driver 104A of the transport motor 104 to transport the printing media P, and so on. Furthermore, the CPU 103 controls the pump driver 500A of the circulation pump 500 (described later), the pump driver 21A of the external pump 21, etc. Note that... Figure 1B The diagram shows a configuration for receiving and processing image data from the main device 400, but the liquid jetting device 50 can perform processing regardless of whether data is supplied from the main device 400.

[0044] <Basic Structure of Liquid Jet Heads>

[0045] Figure 2 This is an exploded perspective view of the liquid injection head 1 according to this embodiment. Figure 3A and Figure 3B yes Figure 2 The cross-sectional view of the liquid injection head 1 along line IIIA-IIIA shown. Figure 3A This is a longitudinal sectional view of the entire liquid injection head 1, and Figure 3B yes Figure 3A The enlarged view of the injection module is shown. It will be primarily referred to in the following text. Figures 2 to 3B And refer to as appropriate Figure 1A and Figure 1B The basic structure of the liquid injection head 1 in this embodiment is described.

[0046] like Figure 2 As shown, the liquid ejection head 1 includes a circulation unit 54 and an ejection unit 3 for ejecting ink supplied from the circulation unit 54 onto the printing medium P. In this embodiment, the liquid ejection head 1 is fixedly supported on the carriage 60 of the liquid ejection device 50 by a positioning unit and an electrical contact (not shown) disposed on the carriage 60. The liquid ejection head 1, together with the carriage 60, is... Figure 1A The printer moves along the main scanning direction (X direction) while simultaneously ejecting ink to print on the printing medium P.

[0047] The external pump 21 connected to the ink cartridge 2, which serves as the ink supply source, includes an ink supply tube 59 (see [link]). Figure 1A Liquid connectors (not shown) are disposed at the ends of each of these ink supply tubes 59. With the liquid ejector head 1 installed in the liquid ejection device 50, the liquid connectors disposed at the ends of the ink supply tubes 59 are hermetically connected to a liquid connector insertion slot 53a, which serves as an inlet on the head housing 53 of the liquid ejector head 1. As a result, an ink supply path is formed extending from the ink cartridge 2 through the external pump 21 to the liquid ejector head 1. In this embodiment, four types of ink are used. Therefore, four sets of ink cartridges 2, external pumps 21, ink supply tubes 59, and circulation units 54 are respectively configured for each type of ink, and four ink supply paths corresponding to each type of ink are formed independently of each other. As described above, the liquid ejection device 50 in this embodiment includes an ink supply system to which ink is supplied from the ink cartridge 2 disposed outside the liquid ejector head 1. Note that the liquid ejection device 50 in this embodiment does not include an ink collection system for collecting ink from the liquid ejector head 1 into the ink cartridge 2. Therefore, the liquid ejector head 1 includes a liquid connector insertion slot 53a for connecting the ink supply tube 59 of the ink cartridge 2, but does not include a connector insertion slot for connecting the tube used to collect ink from the liquid ejector head 1 into the ink cartridge 2. Note that a liquid connector insertion slot 53a is provided for each ink cartridge.

[0048] exist Figure 3A In the accompanying drawings, reference numerals 54B, 54C, 54M, and 54Y denote circulation units for black, cyan, magenta, and yellow inks, respectively. The circulation units have substantially the same construction, and in this embodiment, each circulation unit will be referred to as "circulation unit 54" unless otherwise specified.

[0049] exist Figure 2and Figure 3A In the process, the spraying unit 3 includes two spraying modules 300, a first support member 4, a second support member 7, an electrical wiring component (electrical wiring tape) 5, and an electrical contact substrate 6. Figure 3B As shown, each spraying module 300 includes a silicon substrate 310 having a thickness of 0.5 mm to 1 mm, and a plurality of spraying elements 15 disposed on one surface of the silicon substrate 310. Although not shown in Figure 3B As shown in the figure, but the silicon substrate 310 also includes a plurality of liquid transport elements 1001, which will be described later (see Figure 1). Figure 20A and Figure 20B In this embodiment, the spray element 15 includes an electrothermal conversion element (heater) that generates heat energy as spray energy for spraying liquid. Electrical energy is supplied to each of the spray elements 15 via electrical wiring formed on the silicon substrate 310 using a film deposition technique.

[0050] Furthermore, the nozzle forming member 320 is formed on the surface of the silicon substrate 310. Figure 3B On the lower surface of the substrate 310. In the nozzle forming member 320, a plurality of pressure chambers 12 corresponding to a plurality of ejection elements 15 and a plurality of ejection nozzles 13 for ejecting ink are formed by photolithography. In addition, a common supply channel 18 and a common collection channel 19 are formed in the silicon substrate 310. Furthermore, a supply connection channel 323 and a collection connection channel 324 are formed in the silicon substrate 310. Through the supply connection channel 323, the common supply channel 18 communicates with the pressure chambers 12, and through the collection connection channel 324, the common collection channel 19 communicates with the pressure chambers 12. In this embodiment, an ejection module 300 is configured to eject two types of ink. Specifically, in Figure 3A Of the two injection modules 300 shown, the one located in Figure 3A The left-hand spray module 300 sprays black and cyan ink, while the module located on the left sprays black and cyan ink. Figure 3A The jetting module 300 on the right jets magenta and yellow ink. Note that this combination is merely an example, and any combination of inks can be used. The configuration can be such that one jetting module jets one type of ink, or jets two or more types of ink. The two jetting modules 300 do not need to jet the same number of inks of the same type. The configuration can be such that only one jetting module 300 is included, or that three or more jetting modules 300 are included. Furthermore, in... Figure 3A and Figure 3B In the example shown, two nozzle arrays extending along the Y direction are formed for ink of one color. For each of the plurality of nozzles 13 forming the respective nozzle arrays, a pressure chamber 12, a common supply channel 18, and a common collection channel 19 are formed.

[0051] The ink supply port and ink collection port, which will be described later, are formed on the back side of the silicon substrate 310. Figure 3B (On the upper surface of the middle). Ink is supplied from ink supply channel 48 to multiple common supply channels 18 through ink supply port. Ink is collected from multiple common collection channels 19 into ink collection channel 49 through ink collection port.

[0052] Note that the ink supply port and ink collection port correspond to the openings used for supplying and collecting ink during forward ink circulation, respectively. Specifically, during forward ink circulation, ink is supplied from the ink supply port into the common supply channel 18, and ink is collected from the common collection channel 19 into the ink collection port. Note that ink circulation in the reverse direction is also possible. In this case, ink is supplied from the aforementioned ink collection port into the common collection channel 19, and ink is collected from the common supply channel 18 into the ink supply port.

[0053] like Figure 3A As shown, the back of the injection module 300 ( Figure 3A The upper surface of the middle part is adhesively fixed to one surface of the first support member 4. Figure 3A The ink supply channel 48 and the ink collection channel 49, penetrating from one surface of the first support member 4 to the opposite surface of the first support member 4, are formed in the first support member 4. The opening of the ink supply channel 48 on one side communicates with the aforementioned ink supply port in the silicon substrate 310. The opening of the ink collection channel 49 on one side communicates with the aforementioned ink collection port in the silicon substrate 310. Note that the ink supply channel 48 and the ink collection channel 49 are independently configured for each type of ink.

[0054] Furthermore, it has an opening 7a for inserting the injection module 300 (see...) Figure 2 The second support member 7 is adhesively fixed to one surface of the first support member 4. Figure 3A The electrical wiring component 5, which is to be electrically connected to the ink jetting module 300, is held on the second support member 7. The electrical wiring component 5 is a component for applying electrical signals for ink jetting to the ink jetting module 300. The electrical connection between the ink jetting module 300 and the electrical wiring component 5 is sealed with a sealant (not shown) to protect it from ink corrosion and external impacts.

[0055] Furthermore, the electrical contact substrate 6 is joined to the end 5a of the electrical wiring component 5 by thermo-press bonding with an anisotropic conductive film (not shown) (see [link]). Figure 2 The electrical wiring component 5 and the electrical contact substrate 6 are electrically connected to each other. The electrical contact substrate 6 has an external signal input terminal (not shown) for receiving electrical signals from the liquid injection device 50.

[0056] In addition, the connecting member 8 ( Figure 3AA supply port 88 and a collection port 89 are disposed between the first support member 4 and the circulation unit 54. In the connecting member 8, a supply port 88 and a collection port 89 are formed for various types of ink. Through the supply port 88 and the collection port 89, the ink supply channel 48 and the ink collection channel 49 in the first support member 4, as well as the channel formed in the circulation unit 54, are interconnected. Figure 3A In this configuration, supply port 88B and collection port 89B are used for black ink, while supply port 88C and collection port 89C are used for cyan ink. Additionally, supply port 88M and collection port 89M are used for magenta ink, while supply port 88Y and collection port 89Y are used for yellow ink.

[0057] Note that the openings at one end of the ink supply channel 48 and the ink collection channel 49 in the first support member 4 have small opening areas that match the ink supply port and ink collection port in the silicon substrate 310. On the other hand, the openings at the other end of the ink supply channel 48 and the ink collection channel 49 in the first support member 4 have large shapes, and their opening areas are the same as the opening areas formed in the bonding member 8, to match the channels in the circulation unit 54. This configuration can suppress the increase in channel resistance to the ink collected from each collection channel. Note that the shapes of the openings at one end and the other end of the ink supply channel 48 and the ink collection channel 49 are not limited to the examples above.

[0058] In the liquid jet head 1 with the above configuration, ink supplied to the circulation unit 54 passes through the supply port 88 in the connecting member 8 and the ink supply channel 48 in the first support member 4, and flows from the ink supply port in the jet module 300 into the common supply channel 18. Thereafter, the ink flows from the common supply channel 18 into the pressure chamber 12 through the supply connection channel 323. A portion of the ink flowing into the pressure chamber is ejected from the jet port 13 when the jet element 15 is driven. The remaining ink that is not ejected passes from the pressure chamber 12 through the collection connection channel 324 and the common collection channel 19, and flows from the ink collection port into the ink collection channel 49 in the first support member 4. Subsequently, the ink flowing into the ink collection channel 49 flows into the circulation unit 54 through the collection port 89 in the connecting member 8 and is collected.

[0059] <Components of a Loop Unit>

[0060] Figure 4 This is a schematic external view of a circulation unit 54 for a type of ink used in a printing apparatus according to this embodiment. A filter 110, a first pressure regulating unit 120, a second pressure regulating unit 150, and a circulation pump 500 are arranged in the circulation unit 54. Figure 5 and Figure 6 As shown, these components are connected by channels to form a circulation path for supplying ink to the jet module 300 in the liquid jet head 1 and collecting ink from the jet module 300 in the liquid jet head 1.

[0061] <Circulation path in a liquid jet head>

[0062] Figure 5 This is a schematic longitudinal cross-sectional view showing the circulation path formed in the liquid jet head 1 for one type of ink (one color of ink). For a clearer depiction of the circulation path, simplifications have been made. Figure 5 The relative positions of the components (such as the first pressure regulating unit 120, the second pressure regulating unit 150, and the circulation pump 500) are as follows. Therefore, the relative positions of the components differ from those described later. Figure 19 The relative positions of the components. Incidentally, Figure 6 It is shown schematically. Figure 5 The diagram shows a loop path. (As shown) Figure 5 and Figure 6 As shown, the first pressure regulating unit 120 includes a first valve chamber 121 and a first pressure control chamber 122. The second pressure regulating unit 150 includes a second valve chamber 151 and a second pressure control chamber 152. The first pressure regulating unit 120 is configured such that the controlled pressure therein is higher than the controlled pressure in the second pressure regulating unit 150. In this embodiment, the two pressure regulating units 120 and 150 are used to achieve circulation within a certain pressure range within a circulation path. Moreover, the configuration is such that ink flows through the pressure chamber 12 (jet element 15) at a flow rate corresponding to the pressure difference between the first pressure regulating unit 120 and the second pressure regulating unit 150. Reference will be made below. Figure 5 and Figure 6 Describe the circulation path in liquid jet head 1 and the flow of ink within that path. Note that... Figure 5 and Figure 6 The arrows in the diagram indicate the direction of ink flow.

[0063] First, it will be described how to connect the components in the liquid jet head 1.

[0064] The ink cartridge 2 (see) is stored outside the liquid ejector head 1. Figure 6 The ink in the liquid jet head 1 is transported to the external pump 21 via the ink supply pipe 59 (see ink supply pipe 59). Figure 1A The filter 110 is connected to the circulation unit 54. The filter 110 is arranged in the ink channel upstream of the circulation unit 54. The ink supply path downstream of the filter 110 is connected to the first valve chamber 121 of the first pressure regulating unit 120. The first valve chamber 121 is accessible by a pressure regulating unit 120. Figure 5 The valve 190A shown has a connection port 191A that is open and closed, which is connected to the first pressure control chamber 122.

[0065] The first pressure control chamber 122 is connected to the supply channel 130, the bypass channel 160, and the pump outlet channel 180 of the circulation pump 500. The supply channel 130 is connected to the common supply channel 18 via the ink supply port provided in the injection module 300. The bypass channel 160 is connected to the second valve chamber 151 provided in the second pressure regulating unit 150. The second valve chamber 151 is connected to the common supply channel 18 via the ink supply port provided in the injection module 300. Figure 5 The valve 190B shown has a connection port 191B that connects to the second pressure control chamber 152 when it is open and closed. Note that... Figure 5 and Figure 6 An example is shown below: one end of the bypass channel 160 is connected to the first pressure control chamber 122 of the first pressure regulating unit 120, while the other end of the bypass channel 160 is connected to the second valve chamber 151 of the second pressure regulating unit 150. However, one end of the bypass channel 160 may be connected to the supply channel 130, while the other end of the bypass channel may be connected to the second valve chamber 151.

[0066] The second pressure control chamber 152 is connected to the collection channel 140. The collection channel 140 is connected to the common collection channel 19 via the ink collection port provided in the jetting module 300. The second pressure control chamber 152 is also connected to the circulation pump 500 via the pump inlet channel 170. Note that... Figure 5 In the attached figure, reference numeral 170a indicates the inlet of pump inlet channel 170.

[0067] Next, the flow of ink in the liquid jet head 1 with the above structure will be described. For example... Figure 6 As shown, the ink stored in the ink cartridge 2 is pressurized by the external pump 21 in the liquid jet device 50, becoming a positive pressure ink flow, and is supplied to the circulation unit 54 of the liquid jet head 1.

[0068] Ink supplied to circulation unit 54 passes through filter 110, removing foreign matter such as dust and air bubbles. The ink then flows into first valve chamber 121 disposed in first pressure regulating unit 120. Due to the pressure loss when the ink passes through filter 110, the ink pressure decreases, but the ink pressure is still positive at this time. hereinafter, with valve 190A open, the ink flowing into first valve chamber 121 passes through connection port 191A and flows into first pressure control chamber 122. Due to the pressure loss when the ink passes through connection port 191A, the pressure of the ink flowing into first pressure control chamber 122 switches from positive to negative.

[0069] Next, the flow of ink in the circulation path will be described. The circulation pump 500 operates such that ink drawn in from the pump inlet channel 170 located upstream of the circulation pump 500 is transported to the pump outlet channel 180 located downstream of the circulation pump 500. Therefore, when the pump is driven, ink supplied to the first pressure control chamber 122 flows into the supply channel 130 and the bypass channel 160 together with ink transported from the pump outlet channel 180. In this embodiment, although details will be described later, a piezoelectric diaphragm pump using a piezoelectric element attached to a diaphragm as a drive source is used as a circulation pump capable of transporting liquid. The piezoelectric diaphragm pump is a pump that transports liquid by changing the volume of the pump chamber by inputting a drive voltage to the piezoelectric element and by alternately moving two check valves in response to changes in pressure.

[0070] Ink flowing into supply channel 130 flows into pressure chamber 12 from ink supply port in jet module 300 via common supply channel 18. When jet element 15 is driven (generating heat), a portion of the ink is ejected from jet port 13. Furthermore, any unused ink during ejection flows through pressure chamber 12 and through common collection channel 19. Thereafter, the ink flows into collection channel 140 connected to jet module 300. Ink flowing into collection channel 140 flows into second pressure control chamber 152 of second pressure regulating unit 150.

[0071] On the other hand, ink flowing from the first pressure control chamber 122 into the bypass channel 160 flows into the second valve chamber 151, passes through the connecting port 191B, and then flows into the second pressure control chamber 152. When the circulation pump 500 is driven, ink flowing into the second pressure control chamber 152 through the bypass channel 160 and ink collected from the collection channel 140 are drawn into the circulation pump 500 through the pump inlet channel 170. Subsequently, the ink drawn into the circulation pump 500 is transported to the pump outlet channel 180 and flows back into the first pressure control chamber 122. Thereafter, ink flowing from the first pressure control chamber 122 into the second pressure control chamber 152 through the supply channel 130 and the injection module 300, as well as ink flowing into the second pressure control chamber 152 through the bypass channel 160, flows into the circulation pump 500. Subsequently, the ink is transported from the circulation pump 500 to the first pressure control chamber 122. Thus, ink circulation occurs within the circulation path.

[0072] As described above, in this embodiment, the liquid can circulate through the circulation paths formed in the liquid jet head 1 using the circulation pump 500. This allows for the suppression of ink thickening in the jet module 300 and the deposition of sedimentation components of the color material. Therefore, excellent ink flowability in the jet module 300 and excellent jetting characteristics at the jet nozzle can be maintained.

[0073] Furthermore, in this embodiment, the circulation path is configured to be completed within the liquid ejector head 1. Therefore, compared to the case where the ink circulates between the ink cartridge 2, which is located outside the liquid ejector head 1, and the liquid ejector head 1, the length of the circulation path can be significantly shortened. Thus, a small circulation pump can be used to circulate the ink.

[0074] Furthermore, the design incorporates only a channel for supplying ink between the liquid ejector head 1 and the ink cartridge 2. In other words, a channel for collecting ink from the liquid ejector head 1 into the ink cartridge 2 is not required. Therefore, only an ink supply tube is needed between the ink cartridge 2 and the liquid ejector head 1, and no ink collection tube is required. Consequently, the liquid ejector device 50 has a simpler internal structure with fewer tubes. This allows for a reduction in the overall size of the device. Furthermore, the reduction in the number of tubes reduces ink pressure fluctuations caused by tube oscillation during the main scan of the liquid ejector head 1. Tube oscillation during the main scan of the liquid ejector head 1 increases the drive load on the carriage motor that drives the carriage 60. Therefore, the reduction in the number of tubes reduces the drive load on the carriage motor, simplifying the main scan mechanism, including the carriage motor, etc. Additionally, since ink does not need to be collected from the liquid ejector head into the ink cartridge, the size of the external pump 21 can also be reduced. As described above, according to this embodiment, the size of the liquid ejector device 50 can be reduced, and costs can be lowered.

[0075] <Pressure Regulation Unit>

[0076] Figures 7A to 7C This is a diagram showing an example of a pressure regulating unit. (Refer to...) Figures 7A to 7C The construction and operation of the pressure regulating units (first pressure regulating unit 120 and second pressure regulating unit 150) incorporated into the liquid injection head 1 described above will be described in more detail. Note that the first pressure regulating unit 120 and the second pressure regulating unit 150 have substantially the same construction. Therefore, the following description will be given by taking the first pressure regulating unit 120 as an example. For the second pressure regulating unit 150, in Figures 7A to 7C Only the reference numerals corresponding to the parts of the first pressure regulating unit are shown in the figures. In the case of the second pressure regulating unit 150, the first valve chamber 121 and the first pressure control chamber 122 described below will be read as the second valve chamber 151 and the second pressure control chamber 152, respectively.

[0077] The first pressure regulating unit 120 has a first valve chamber 121 and a first pressure control chamber 122 formed in a cylindrical housing 125. The first valve chamber 121 and the first pressure control chamber 122 are separated by a partition 123 disposed within the cylindrical housing 125. However, the first valve chamber 121 communicates with the first pressure control chamber 122 through a communication port 191 formed in the partition 123. A valve 190 is disposed in the first valve chamber 121, which switches between allowing communication between the first valve chamber 121 and the first pressure control chamber 122 through the communication port 191 and preventing such communication. The valve 190 is held in a position opposite to the communication port 191 by a valve spring 200 and has a configuration that allows it to be in close contact with the partition 123 by a biasing force from the valve spring 200. The valve 190 prevents ink from flowing through the communication port 191 by being in close contact with the partition 123. Note that the portion of valve 190 that contacts partition 123 is preferably formed of an elastic member, thereby enhancing the tightness of the contact with partition 123. Furthermore, valve shaft 190a, which will be inserted through the communication port 191, is disposed in a protruding manner on the central portion of valve 190. By pressing valve shaft 190a against the biasing force from valve spring 200, valve 190 separates from partition 123, thereby allowing ink to flow through communication port 191. In the following text, the state in which valve 190 prevents ink from flowing through communication port 191 will be referred to as the "closed state," and the state in which ink can flow through communication port 191 will be referred to as the "open state."

[0078] The opening of the cylindrical housing 125 is closed by the flexible member 230 and the pressing plate 210. The flexible member 230, the pressing plate 210, the peripheral wall of the housing 125d, and the partition 123 form a first pressure control chamber 122. The pressing plate 210 is configured to be displaceable with the displacement of the flexible member 230. While there are no particular limitations on the materials of the pressing plate 210 and the flexible member 230, for example, the pressing plate 210 can be made as a molded resin part, and the flexible member 230 can be made of a resin film. In this case, the pressing plate 210 can be fixed to the flexible member 230 by heat welding.

[0079] A pressure adjusting spring 220 (biasing member) is disposed between the pressing plate 210 and the partition plate 123. For example... Figure 7AAs shown, the pressing plate 210 and the flexible member 230 are biased by the biasing force from the pressure regulating spring 220 in the direction of increasing internal volume of the first pressure control chamber 122. Furthermore, when the pressure in the first pressure control chamber 122 decreases, the pressing plate 210 and the flexible member 230 resist the pressure from the pressure regulating spring 220 and displace in the direction of decreasing internal volume of the first pressure control chamber 122. Subsequently, when the internal volume of the first pressure control chamber 122 decreases to a certain volume, the pressing plate 210 abuts against the valve shaft 190a of the valve 190. When the internal volume of the first pressure control chamber 122 decreases further, the valve 190, together with the valve shaft 190a, moves against the biasing force from the valve spring 200, thereby separating from the partition 123. As a result, the communication port 191 switches to the open state. Figure 7B (State).

[0080] In this embodiment, the connection in the circulation path is configured such that the pressure in the first valve chamber 121 is greater than the pressure in the first pressure control chamber 122 when the connection port 191 is switched to the open state. In this way, when the connection port 191 is switched to the open state, ink flows from the first valve chamber 121 into the first pressure control chamber 122. The inflow of ink causes the flexible member 230 and the pressing plate 210 to displace in the direction of increasing internal volume of the first pressure control chamber 122. As a result, the pressing plate 210 separates from the valve shaft 190a of the valve 190, and the valve 190 is brought into close contact with the partition 123 by the biasing force from the valve spring 200, causing the connection port 191 to switch to the closed state. Figure 7C (State).

[0081] As described above, in the first pressure regulating unit 120 of this embodiment, when the pressure in the first pressure control chamber 122 decreases below a certain pressure (for example, when the negative pressure increases), ink flows from the first valve chamber 121 through the communication port 191. This configuration limits further decrease in pressure in the first pressure control chamber 122. Therefore, the pressure in the first pressure control chamber 122 is controlled to be maintained within a certain range.

[0082] The pressure in the first pressure control chamber 122 will be described in more detail next.

[0083] Consider the following state: as described above, the flexible member 230 and the pressing plate 210 are displaced according to the pressure in the first pressure control chamber 122, such that the pressing plate 210 abuts against the valve shaft 190a and the communication port 191 is in the open state. Figure 7B (The state of the press plate 210). The relationship between the forces acting on the press plate 210 at this time is expressed by the following equation 1.

[0084] P2×S2+F2+(P1-P2)×S1+F1=0...Equation 1

[0085] Furthermore, Equation 1 for P2 is summarized as follows.

[0086] P2=-(F1+F2+P1×S1) / (S2-S1)...Equation 2

[0087] P1: Pressure in the first valve chamber 121 (metered pressure)

[0088] P2: Pressure (metered pressure) in the first pressure control chamber 122

[0089] F1: Spring force of valve spring 200

[0090] F2: Spring force of pressure regulating spring 220

[0091] S1: Pressure-bearing area of ​​valve 190

[0092] S2: The pressure area of ​​the pressing plate 210

[0093] Here, the directions in which the spring force F1 of the valve spring 200 and the spring force F2 of the pressure regulating spring 220 push the valve 190 and the pressing plate 210 are defined as the positive direction. Figures 7A to 7C (to the right in the middle). Moreover, the structure is such that the pressure P1 in the first valve chamber 121 and the pressure P2 in the first pressure control chamber 122 satisfy the relationship P1≥P2.

[0094] The pressure P2 in the first pressure control chamber when the connection port 191 is switched to the open state is determined by Equation 2. Due to the construction that satisfies the relationship P1 ≥ P2, ink flows from the first valve chamber 121 into the first pressure control chamber 122 when the connection port 191 is switched to the open state. As a result, the pressure P2 in the first pressure control chamber 122 does not decrease further, and the pressure P2 remains within a certain range.

[0095] On the other hand, such as Figure 7C As shown, the relationship between the forces acting on the press plate 210 when the press plate 210 is not in contact with the valve shaft 190a and the communication port 191 is switched to the closed state is represented by the following equation 3.

[0096] P3×S3+F3=0...Equation 3

[0097] Here, we summarize Equation 3 for P3 as follows.

[0098] P3 = -F3 / S3...Equation 4

[0099] F3: The spring force of the pressure regulating spring 220 when the pressing plate 210 is not in contact with the valve shaft 190a.

[0100] P3: The pressure (metering pressure) in the first pressure control chamber 122 when the pressure plate 210 is not in contact with the valve shaft 190a.

[0101] S3: The pressure-bearing area of ​​the pressing plate 210 when it is not in contact with the valve 190.

[0102] Here, Figure 7C The pressing plate 210 and the flexible member 230 are shown along... Figure 7C The pressure P3 in the first pressure control chamber 122, the spring force F3 of the pressure adjusting spring 220, and the pressure-bearing area S3 of the pressing plate 210 are determined by the pressing plate 210 and the flexible member 230 in the rightward direction to the limit of their displacement. Figure 7C The displacement varies with the displacement of the state. Specifically, the displacement of the pressing plate 210 and the flexible member 230 relative to the state... Figure 7C They themselves are located in Figure 7A In the case on the left side, the pressure-bearing area S3 of the pressing plate 210 is smaller, and the spring force F3 of the pressure regulating spring is larger. Therefore, the pressure P3 in the first pressure control chamber 122 is smaller according to the relationship in Equation 4. Therefore, using Equations 2 and 4, the pressure in the first pressure control chamber 122 is smaller from... Figure 7B state towards Figure 7C The pressure gradually increases during the transition between states (i.e., the negative pressure weakens as it approaches the positive pressure side). Specifically, as the pressure plate 210 and flexible member 230 gradually move to the right from the open state of the communication port 191 towards the limit of displacement of the internal volume of the first pressure control chamber, the pressure in the first pressure control chamber 122 gradually increases. In other words, the negative pressure weakens.

[0103] <Circulation Pump>

[0104] Next, we will refer to Figure 8A and Figure 8B as well as Figure 9 The construction and operation of each circulation pump 500 incorporated in the above liquid injection head 1 are described in detail.

[0105] Figure 8A and Figure 8B This is a 3D view of the Circulation Pump 500. Figure 8A This is a perspective view showing the front of the circulation pump 500. Figure 8BThis is a perspective view showing the rear side of the circulating pump 500. The housing of the circulating pump 500 includes a pump housing 505 and a cover 507 fixed to the pump housing 505. The pump housing 505 includes a housing body 505a and a channel connecting member 505b adhesively fixed to the outer surface of the housing body 505a. In each of the housing body 505a and the channel connecting member 505b, a pair of through holes communicating with each other are formed at two different locations. One of the through holes in the pair of through holes, located at one location, forms a pump supply hole 501. The other hole in the pair of through holes, located at the other location, forms a pump discharge hole 502. The pump supply hole 501 is connected to a pump inlet passage 170 connected to a second pressure control chamber 152. The pump discharge hole 502 is connected to a pump outlet passage 180 connected to a first pressure control chamber 122. Ink supplied from the pump supply hole 501 passes through a pump chamber 503, which will be described later (see [link to relevant documentation]). Figure 9 ), and is discharged from pump discharge port 502.

[0106] Figure 9 yes Figure 8A The diagram shows a cross-sectional view of the circulating pump 500 along line IX-IX. A diaphragm 506 is joined to the inner surface of the pump housing 505, and a pump chamber 503 is formed between the diaphragm 506 and a recess formed in the inner surface of the pump housing 505. The pump chamber 503 communicates with a pump supply port 501 and a pump discharge port 502 formed in the pump housing 505. Furthermore, a check valve 504a is disposed at the middle portion of the pump supply port 501. A check valve 504b is disposed at the middle portion of the pump discharge port 502. Specifically, the check valve 504a is arranged such that a portion thereof can be within the space 512a formed in the middle portion of the pump supply port 501. Figure 9 The check valve 504a is arranged such that a portion of it can move to the left within the space 512b formed in the middle of the pump discharge port 502. Figure 9 Move to the right in the middle.

[0107] When the diaphragm 506 displaces to increase the volume of the pump chamber 503, the pump chamber 503 is depressurized. In response to this displacement, the check valve 504a separates from the opening of the pump supply port 501 in the space 512a (i.e., along...). Figure 9 (Moving to the left in the middle). By separating from the opening of the pump supply port 501 in space 512a, the check valve 504a switches to an open state that allows ink to flow through the pump supply port 501. When the diaphragm 506 displaces to reduce the volume of the pump chamber 503, the pump chamber 503 is pressurized. In response to this displacement, the check valve 504a comes into close contact with the wall surface surrounding the opening of the pump supply port 501. The check valve 504a is thus in a closed state that prevents ink from flowing through the pump supply port 501.

[0108] On the other hand, when the pump chamber 503 is depressurized, the check valve 504b comes into close contact with the wall surface surrounding the opening in the pump housing 505, thereby switching to a closed state where the check valve 504b prevents ink from flowing through the pump discharge port 502. Furthermore, when the pump chamber 503 is pressurized, the check valve 504b separates from the opening in the pump housing 505 and moves toward the space 512b (i.e., along...). Figure 9 (Move to the right in the middle), thereby allowing ink to flow through the pump discharge hole 502.

[0109] Note that the materials of each of the check valves 504a and 504b need only be materials that can deform under the pressure in the pump chamber 503. For example, the materials of each of the check valves 504a and 504b can be made of elastic materials such as EPDM or elastomers, or membranes or sheets of polypropylene, etc. However, the materials are not limited to these.

[0110] As described above, the pump chamber 503 is formed by joining the pump housing 505 with the diaphragm 506. Therefore, the pressure in the pump chamber 503 changes with the deformation of the diaphragm 506. For example, when the diaphragm 506 displaces toward the pump housing 505 (towards...) Figure 9 When the volume of pump chamber 503 is reduced due to the rightward displacement of the pump chamber, the pressure in pump chamber 503 increases. As a result, check valve 504b, which is arranged to face pump discharge port 502, switches to the open state, allowing ink to be discharged from pump chamber 503. At this time, check valve 504a, which is arranged to face pump supply port 501, comes into close contact with the wall surface around pump supply port 501, thereby preventing ink from flowing back from pump chamber 503 into pump supply port 501.

[0111] Conversely, as the diaphragm 506 displaces in the direction of widening of the pump chamber 503, the pressure in the pump chamber 503 decreases. As a result, the check valve 504a, arranged facing the pump supply port 501, switches to the open state, allowing ink to be supplied into the pump chamber 503. At this time, the check valve 504b arranged in the pump discharge port 502 comes into close contact with the wall surface surrounding the opening formed in the pump housing 505 to close the opening. This prevents ink from flowing back from the pump discharge port 502 into the pump chamber 503.

[0112] As described above, in the circulating pump 500, ink is drawn in and discharged when the diaphragm 506 deforms, thereby changing the pressure in the pump chamber 503. At this time, if air bubbles have already entered the pump chamber 503, the displacement of the diaphragm 506 due to the expansion or contraction of the bubbles changes the pressure in the pump chamber 503 to a small extent. Therefore, the amount of liquid to be transported is reduced. To address this phenomenon, the pump chamber 503 is arranged parallel to gravity, allowing air bubbles that have entered the pump chamber 503 to easily accumulate at the top of the pump chamber 503. Furthermore, the pump discharge port 502 is arranged above the center of the pump chamber 503. This improves the ease of discharging air bubbles from the pump and thus stabilizes the flow rate.

[0113] <Ink flow within the liquid jet nozzle>

[0114] Figures 10A to 10E This is a diagram depicting the flow of ink within a liquid ejector head. (Refer to...) Figures 10A to 10E This describes the ink circulation within the liquid ejector head 1. To more clearly illustrate the ink circulation path, a simplified diagram is provided. Figures 10A to 10E The relative positions of the components (such as the first pressure regulating unit 120, the second pressure regulating unit 150, and the circulation pump 500) are as described later. Therefore, the relative positions of the components differ from those mentioned later. Figure 19 The relative positions of the components. Figure 10A This schematically illustrates the ink flow during a printing operation where ink is ejected from nozzle 13. Note that... Figure 10A The arrows in the diagram indicate the ink flow. In this embodiment, both the external pump 21 and the circulation pump 500 are started to drive in order to begin the printing operation. The external pump 21 and the circulation pump 500 do not need to be driven together and can be driven independently of each other. In this embodiment, the circulation pump 500 is driven on demand based on the determination of the CPU 103.

[0115] During the printing operation, the circulation pump 500 is essentially on (driven), causing ink flowing from the first pressure control chamber 122 to flow into the supply channel 130 and the bypass channel 160. The ink that has flowed into the supply channel 130 passes through the ejection module 300 and subsequently flows into the collection channel 140. Thereafter, ink is supplied to the second pressure control chamber 152.

[0116] On the other hand, ink that has flowed from the first pressure control chamber 122 into the bypass channel 160 flows into the second pressure control chamber 152 through the second valve chamber 151. The ink that has flowed into the second pressure control chamber 152 passes through the pump inlet channel 170, the circulation pump 500, and the pump outlet channel 180, and then flows back into the first pressure control chamber 122. At this time, based on the relationship in Equation 2 mentioned above, the controlled pressure in the first valve chamber 121 is set higher than the controlled pressure in the first pressure control chamber 122. Therefore, the ink in the first pressure control chamber 122 does not flow back into the first valve chamber 121, but is instead supplied back to the injection module 300 through the supply channel 130. The ink that has flowed into the injection module 300 flows back into the first pressure control chamber 122 through the collection channel 140, the second pressure control chamber 152, the pump inlet channel 170, the circulation pump 500, and the pump outlet channel 180. Ink circulation is performed within the liquid injection head 1 as described above.

[0117] In the above ink circulation, the pressure difference between the controlled pressure in the first pressure control chamber 122 and the controlled pressure in the second pressure control chamber 152 determines the amount of ink circulating (flow rate) within the ejection module 300. Furthermore, this pressure difference is set to obtain a circulation amount capable of suppressing ink thickening near the ejection nozzle in the ejection module 300. Incidentally, the amount of ink consumed during printing is supplied from the ink cartridge 2 to the first pressure control chamber 122 through the filter 110 and the first valve chamber 121. How the consumed ink is supplied will now be described in detail. The amount of ink consumed during printing decreases as ink in the circulation path decreases. Therefore, the pressure in the first pressure control chamber 122 decreases, resulting in a decrease in ink in the first pressure control chamber. When the ink in the first pressure control chamber 122 decreases, the internal volume of the first pressure control chamber 122 decreases accordingly. When the internal volume of the first pressure control chamber 122 decreases, the connection port 191A switches to the open state, allowing ink to be supplied from the first valve chamber 121 to the first pressure control chamber 122. When ink supplied from the first valve chamber 121 passes through the connection port 191A, a pressure loss occurs in the supplied ink. As the ink flows into the first pressure control chamber 122, the positive pressure of the ink switches to a negative pressure. As ink flows from the first valve chamber 121 into the first pressure control chamber 122, the pressure in the first pressure control chamber increases. As the internal volume of the first pressure control chamber increases, the connection port 191A switches to a closed state. As described above, the connection port 191A repeatedly switches between an open and closed state according to ink consumption. Incidentally, when ink is not consumed, the connection port 191A is kept in the closed state.

[0118] Figure 10BThe diagram schematically illustrates the ink flow immediately following the switching off (stopped) state of the circulation pump 500. When the circulation pump 500 switches to the off state, the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152 are both controlled pressures used in the printing operation. Therefore, the ink flows according to the pressure difference between the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152, such as... Figure 10B The flow is as shown. Specifically, a continuous flow of ink is generated from the first pressure control chamber 122 to the injection module 300 through the supply channel 130, and subsequently to the second pressure control chamber 152 through the collection channel 140. In addition, a continuous flow of ink is generated from the first pressure control chamber 122 to the second pressure control chamber 152 through the bypass channel 160 and the second valve chamber 151.

[0119] The amount of ink that moves from the first pressure control chamber 122 to the second pressure control chamber 152 through the ink flow is supplied from the ink cartridge 2 to the first pressure control chamber 122 through the filter 110 and the first valve chamber 121. Therefore, the internal volume of the first pressure control chamber 122 is maintained constant. According to the relationship in Equation 2 mentioned above, with the internal volume of the first pressure control chamber 122 remaining constant, the spring force F1 of the valve spring 200, the spring force F2 of the pressure regulating spring 220, the pressure-receiving area S1 of the valve 190, and the pressure-receiving area S2 of the pressing plate 210 are maintained constant. Therefore, the pressure in the first pressure control chamber 122 is determined based on the change in the pressure (metering pressure) P1 in the first valve chamber 121. Therefore, with the pressure P1 in the first valve chamber 121 remaining unchanged, the pressure P2 in the first pressure control chamber 122 is maintained at the same pressure as the controlled pressure during the printing operation.

[0120] On the other hand, the pressure in the second pressure control chamber 152 changes over time according to the change in internal volume caused by the inflow of ink from the first pressure control chamber 122. Specifically, the pressure in the second pressure control chamber 152 changes according to Equation 2 until the connecting port 191... Figure 10B The state is changed to the closed state to prevent such... Figure 10C The connection between the second valve chamber 151 and the second pressure control chamber 152 is shown. Thereafter, the pressure plate 210 does not abut against the valve shaft 190a, causing the connection port 191 to switch to the closed state. Subsequently, as... Figure 10D As shown, ink flows from collection channel 140 into the second pressure control chamber 152. This ink inflow causes displacement of the pressing plate 210 and the flexible member 230. The pressure in the second pressure control chamber 152 varies according to Equation 4. Specifically, the pressure increases until the internal volume of the second pressure control chamber 152 reaches its maximum.

[0121] Note that once it reaches... Figure 10CIn this state, there is no longer any flow of ink from the first pressure control chamber 122 to the second pressure control chamber 152 via the bypass channel 160 and the second valve chamber 151. Therefore, ink flow to the second pressure control chamber 152 via the collection channel 140 only occurs after the ink in the first pressure control chamber 122 is supplied to the ejection module 300 via the supply channel 130. As described above, ink moves from the first pressure control chamber 122 to the second pressure control chamber 152 according to the pressure difference between the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152. Therefore, when the pressure in the second pressure control chamber 152 becomes equal to the pressure in the first pressure control chamber 122, the ink stops moving.

[0122] Furthermore, when the pressure in the second pressure control chamber 152 is equal to the pressure in the first pressure control chamber 122, the second pressure control chamber 152 expands to... Figure 10D The state shown. In the second pressure control chamber 152, as indicated. Figure 10D Under the expansion shown, a reservoir capable of holding ink is formed in the second pressure control chamber 152. Note that after stopping the circulation pump 500... Figure 10D The transition between states takes approximately 1 to 2 minutes. This time may vary depending on the shape and size of the channel and the characteristics of the ink. When the circulation pump 500 is in... Figure 10D When driven while maintaining ink in the reservoir, the ink in the reservoir is supplied to the first pressure control chamber 122 by the circulation pump 500. Therefore, as shown... Figure 10E As shown, the amount of ink in the first pressure control chamber 122 increases, causing the flexible member 230 and the pressing plate 210 to displace in the expansion direction. Subsequently, as the circulation pump 500 is continuously driven, the state inside the circulation path changes to... Figure 10A The state shown.

[0123] Note that in the above description, it has already been stated that... Figure 10A This describes an example of ink circulation during a printing operation. However, as mentioned above, ink can circulate even without a printing operation. Even in this case, ink circulates in response to the driving and stopping of the circulation pump 500. Figures 10A to 10E The flow is shown.

[0124] Furthermore, as described above, in this embodiment, the following example has been used: the connection port 191B in the second pressure regulating unit 150 is switched to an open state when ink is circulated by driving the circulation pump 500, and switched to a closed state when ink circulation stops. However, this embodiment is not limited to this example. The controlled pressure can be set such that even when ink is circulated by driving the circulation pump 500, the connection port 191B in the second pressure regulating unit 150 remains closed. This will be described in detail below along with the function of the bypass channel 160.

[0125] In order to avoid the effects of strong negative pressure, for example, if the negative pressure generated inside the circulation path becomes stronger than a preset value, the injection module 300 is provided with a bypass channel 160 connecting the first pressure regulating unit 120 and the second pressure condition unit 150. The bypass channel 160 is also provided to supply ink to the pressure chamber 12 from both the supply channel 130 and the collection channel 140.

[0126] First, a description of an example will be given below: By configuring a bypass channel 160, the influence of negative pressure exceeding a preset value on the ejection module 300 is avoided. For example, changes in ambient temperature sometimes alter the properties of the ink (e.g., viscosity). When the viscosity of the ink changes, the pressure loss within the circulation path also changes. For example, when the viscosity of the ink decreases, the amount of pressure loss within the circulation path decreases. As a result, the flow rate of the circulation pump 500, driven with a constant drive amount, increases, and the flow rate through the ejection module 300 increases. Here, the ejection module 300 is maintained at a constant temperature by a temperature regulating mechanism (not shown). Therefore, even if the ambient temperature changes, the viscosity of the ink inside the ejection module 300 remains constant. The viscosity of the ink inside the ejection module 300 remains constant, while the flow rate of the ink flowing through the ejection module 300 increases, and therefore the negative pressure in the ejection module 300 becomes correspondingly stronger due to flow resistance. If the negative pressure in the injection module 300 becomes stronger than the preset value described above, there is a possibility that the meniscus in the injection port 13 may be damaged and ambient air may be drawn into the circulation path, which may result in the inability to perform normal injection. Moreover, even if the meniscus is not damaged, there is still a possibility that the negative pressure in the pressure chamber 12 may become stronger than the predetermined level and affect the injection.

[0127] For these reasons, in this embodiment, a bypass channel 160 is formed in the circulation path. By providing the bypass channel 160, ink flows through it when the negative pressure is stronger than a preset value. Therefore, the pressure in the ejection module 300 remains constant. Thus, for example, the controlled pressure can be set such that even when the circulation pump 500 is driven, the connection port 191B in the second pressure regulating unit 150 is kept closed. Furthermore, the controlled pressure in the second pressure regulating unit 150 can be set such that when the negative pressure becomes stronger than a preset value, the connection port 191B in the second pressure regulating unit 150 switches to an open state. In other words, the connection port 191B can be kept closed when the circulation pump 500 is driven, as long as the meniscus does not collapse or the predetermined negative pressure is maintained even if the pump flow rate changes due to viscosity variations caused by environmental changes.

[0128] The following example will be described: A bypass channel 160 is provided to supply ink to the pressure chamber 12 from both the supply channel 130 and the collection channel 140. The pressure in the circulation path may fluctuate due to the ejection operation of the ejection element 15. This is because the ejection operation generates a force that draws ink into the pressure chamber.

[0129] The following description will depict the fact that, under continuous high-load printing conditions, ink is supplied to the pressure chamber 12 from both the supply channel 130 side and the collection channel 140 side. While the definition of "load" may vary depending on various conditions, in the following text, a state of printing at a 1200 dpi grid with a single 4pl ink droplet will be considered 100%. "High-load printing" is, for example, printing performed at 100% load.

[0130] Under continuous high-load printing, the amount of ink flowing from pressure chamber 12 into the second pressure control chamber 152 through collection channel 140 decreases. On the other hand, circulation pump 500 causes ink to flow out at a constant rate. This disrupts the balance between inflow and outflow in the second pressure control chamber 152. As a result, the amount of ink inside the second pressure control chamber 152 decreases, and the negative pressure in the second pressure control chamber 152 becomes stronger, causing the second pressure control chamber 152 to shrink. When the negative pressure in the second pressure control chamber 152 becomes stronger, the amount of ink flowing into the second pressure control chamber 152 through bypass channel 160 increases, and the second pressure control chamber 152 becomes stable in a state of balance between inflow and outflow. Therefore, the negative pressure in the second pressure control chamber 152 becomes stronger depending on the load. Moreover, as described above, in the configuration where the connection port 191B is in the closed state when the circulation pump 500 is driven, the connection port 191B switches to the open state according to the load, causing ink to flow into the second pressure control chamber 152 from bypass channel 160.

[0131] Furthermore, as high-volume printing continues, the inflow from pressure chamber 12 through collection channel 140 to the second pressure control chamber 152 decreases, and conversely, the inflow from connector 191B through bypass channel 160 to the second pressure control chamber 152 increases. As this state progresses further, the amount of ink flowing from pressure chamber 12 through collection channel 140 into the second pressure control chamber 152 reaches zero, such that the ink flowing from connector 191B is all the ink flowing out to circulation pump 500. As this state progresses further, ink returns from the second pressure control chamber 152 to pressure chamber 12 through collection channel 140. In this state, ink flowing from the second pressure control chamber 152 into circulation pump 500 and ink flowing from the second pressure control chamber 152 into pressure chamber 12 will flow from connector 191B through bypass channel 160 into the second pressure control chamber 152. In this case, ink from supply channel 130 and ink from collection channel 140 are filled into pressure chamber 12 and ejected from it.

[0132] Note that this ink backflow occurring under high print load is a phenomenon caused by the installation of the bypass channel 160. Furthermore, as described above, an example has been given where the connection port 191B in the second pressure regulating unit is switched to the open state for ink backflow. However, ink backflow can also occur with the connection port 191B in the second pressure regulating unit in the open state. Moreover, in a configuration without a second pressure regulating unit, the aforementioned ink backflow can also occur by installing the bypass channel 160.

[0133] <Construction of the jet unit>

[0134] Figure 11A and Figure 11B This is a schematic diagram showing the circulation path of ink of one color in the spraying unit 3 of this embodiment. Figure 11A This is an exploded perspective view of the jetting unit 3 as viewed from the side of the first support member 4. Figure 11B This is an exploded perspective view of the injection unit 3 as seen from the side of the injection module 300. Note that in Figure 11A and Figure 11B The arrows, indicated as "in" and "out," show the flow of ink, and the description will only apply to one color; however, other colors of ink flow similarly. Furthermore, in Figure 11A and Figure 11B The illustrations of the second support member 7 and the electrical wiring member 5 are omitted, and their descriptions are also omitted in the subsequent description of the construction of the injection unit. Furthermore, for Figure 11A The first support member 4 in the middle is shown along Figure 3A The cross-section of line XI-XI. Each spray module 300 includes a spray element substrate 340 and an opening plate 330. Figure 12 This is a diagram showing the opening plate 330. Figure 13 This is a diagram showing the jetting element substrate 340.

[0135] The injection unit 3 is connected to the coupling member 8 (see...) Figure 3A Ink is supplied from each circulation unit 54. The ink path returning to the coupling member 8 after passing through the coupling member 8 will now be described. Note that the coupling member 8 is omitted from the figures mentioned below.

[0136] Each ejection module 300 includes an ejection element substrate 340 and an opening plate 330, which serve as a silicon substrate 310, and further includes an ejection nozzle forming member 320. The ejection element substrate 340, the opening plate 330, and the ejection nozzle forming member 320 are stacked and joined so that the channels of each ink are interconnected to form the ejection module 300. The ejection module 300 is supported on a first support member 4. An ejection unit 3 is formed by supporting each ejection module 300 on the first support member 4. The ejection element substrate 340 includes the ejection nozzle forming member 320, which includes a plurality of ejection nozzle arrays, which are a plurality of ejection nozzles 13 forming a line. A portion of the ink supplied through the ink channels in the ejection module 300 is ejected from the ejection nozzles 13. Unejected ink is collected through the ink channels in the ejection module 300.

[0137] like Figure 11A and Figure 11B as well as Figure 12 As shown, the opening plate 330 includes a plurality of ink supply ports 311 arranged in an array and a plurality of ink collection ports 312 arranged in an array. As... Figure 13 and Figures 14A to 14C As shown, the jetting element substrate 340 includes a plurality of arrayed supply connection channels 323 and a plurality of arrayed collection connection channels 324. The jetting element substrate 340 also includes a common supply channel 18 communicating with the plurality of supply connection channels 323, and a common collection channel 19 communicating with the plurality of collection connection channels 324. The ink supply channel 48 and ink collection channel 49 are arranged in the first support member 4 (see...). Figure 3A The ink supply channel 48 is connected to the channels arranged in each of the ink injection modules 300 to form the ink channel inside the ink injection unit 3. The support member supply port 211 is an opening in the cross-section forming the ink supply channel 48. The support member collection port 212 is an opening in the cross-section forming the ink collection channel 49.

[0138] The ink to be supplied to the jetting unit 3 is drawn from the circulation unit 54 (see...). Figure 3A The ink supply channel 48 (see) is supplied from the side to the first support member 4. Figure 3AOn the side. Ink flowing through the support member supply port 211 in the ink supply channel 48 passes through the ink supply channel 48 (see side). Figure 3A The ink supply port 311 in the opening plate 330 is supplied to the common supply channel 18 in the jet element substrate 340 and enters the supply connection channel 323. The channel so far is the supply-side channel. Thereafter, the ink passes through the pressure chamber 12 in the jet forming member 320 (see...). Figure 3B And it flows into the collection connection channel 324 of the collection side channel. Details of the ink flow in the pressure chamber 12 will be described below.

[0139] In the collection side channel, the ink that has entered the collection connection channel 324 flows into the common collection channel 19. Thereafter, the ink flows from the common collection channel 19 through the ink collection port 312 in the opening plate 330 into the ink collection channel 49 in the first support member 4, and is collected into the circulation unit 54 through the support member collection port 212.

[0140] The area of ​​the opening plate 330 where there is no ink supply port 311 or ink collection port 312 corresponds to the area of ​​the first support member 4 used to separate the support member supply port 211 and the support member collection port 212. Furthermore, the first support member 4 does not need to have openings in these areas. Such areas are used as engagement areas when the jetting module 300 is engaged with the first support member 4.

[0141] exist Figure 12 In the opening plate 330, an array of multiple openings arranged along the X direction is arranged side-by-side along the Y direction, with openings for supply (IN) and openings for collection (OUT) alternately arranged along the Y direction, while being shifted from each other by half a pitch along the X direction. Figure 13 In the ink jetting element substrate 340, a common supply channel 18 communicating with a plurality of supply connection channels 323 arrayed along the Y direction and a common collection channel 19 communicating with a plurality of collection connection channels 324 arrayed along the Y direction are alternately arranged along the X direction. The common supply channel 18 and the common collection channel 19 are separated by the type of ink. Furthermore, the number of jetting nozzle arrays for each color determines the number of common supply channels 18 and common collection channels 19 to be arranged. Moreover, the number of arranged supply connection channels 323 and the number of arranged collection connection channels 324 correspond to the number of jetting nozzles 13. Note that a one-to-one correspondence is not necessarily required, and a single supply connection channel 323 and a single collection connection channel 324 can correspond to multiple jetting nozzles 13.

[0142] Each jetting module 300 is formed as described above by stacking and joining an opening plate 330 with a jetting element substrate 340, such that the channels of each ink are interconnected and supported on a first support member 4. As a result, an ink channel including a supply channel and a collection channel is formed as described above.

[0143] Figures 14A to 14C This is a cross-sectional view showing the flow of ink at different parts of the jetting unit 3. Figure 14A It is along Figure 11A The image shows a cross-section cut by lines XIVa-XIVa, and also shows a cross-section of the portion where the ink supply channel 48 of the jetting unit 3 communicates with the ink supply port 311. Figure 14B It is along Figure 11A The image shows a cross-section cut along line XIVb-XIVb, and also shows a cross-section of the portion where the ink collection channel 49 and the ink collection port 312 of the jetting unit 3 communicate with each other. Furthermore, Figure 14C It is along Figure 11A The cross-section is shown by line XIVc-XIVc, and the cross-section of the portion where the ink supply port 311 and ink collection port 312 are not connected to the channel in the first support member 4 is also shown. Note that in Figures 14A to 14C The liquid transport element 1001 is omitted.

[0144] like Figure 14A As shown, the ink supply channel supplies ink from the portion where the ink supply channel 48 in the first support member 4 overlaps with and communicates with the ink supply port 311 in the opening plate 330. Furthermore, as... Figure 14B As shown, the ink collection channel collects ink from the portion where the ink collection channel 49 in the first support member 4 overlaps with and communicates with the ink collection port 312 in the opening plate 330. Furthermore, as... Figure 14C As shown, the spraying unit 3 partially has areas where no openings are provided in the opening plate 330. In such areas, neither ink is supplied nor collected between the spraying element substrate 340 and the first support member 4. Figure 14A As shown, ink is supplied at the area equipped with ink supply port 311. Figure 14B As shown, ink is collected in the area where the ink collection port 312 is provided. Note that this embodiment has been described as an example using a configuration with an opening plate 330, but a configuration without the opening plate 330 can be used. For example, a configuration can be used in which channels corresponding to the ink supply channel 48 and the ink collection channel 49 are formed in the first support member 4, and the jetting element substrate 340 is attached to the first support member 4.

[0145] Figure 15A and Figure 15B This is a cross-sectional view showing the vicinity of the injection port 13 in the injection module 300. Figure 16A and Figure 16BThis is a cross-sectional view of a jetting module with a configuration where the common supply channel 18 and the common collection channel 19 are widened along the X direction, as a comparative example. Note that in Figure 15A and Figure 15B as well as Figure 16A and Figure 16B The bold arrows shown in the common supply channel 18 and common collection channel 19 indicate the oscillating motion of ink that occurs in the configuration using the serial liquid jetting device 50. When the jetting element 15 is driven, ink supplied to the pressure chamber 12 through the common supply channel 18 and the supply connection channel 323 is ejected from the jetting nozzle 13. When the jetting element 15 is not driven, the ink is collected from the pressure chamber 12 into the common collection channel 19 through the collection connection channel 324, which serves as a collection channel.

[0146] When ink circulating as described above is ejected in a configuration using a serial liquid ejection device 50, the ink ejection is largely affected by the oscillating motion of the ink within the ink channel caused by the main scan of the liquid ejection head 1. Specifically, the effect of the oscillating motion of the ink within the ink channel manifests as differences in the amount of ink ejected and deviations in the ejection direction. Figure 16A and Figure 16B As shown, when the common supply channel 18 and common collection channel 19 have a cross-sectional shape that is wide in the X direction, which is the main scanning direction, the ink inside the common supply channel 18 and common collection channel 19 is more likely to receive inertial forces in the main scanning direction, causing the ink to oscillate significantly. This leads to the possibility that the oscillating motion of the ink may affect the ink ejection from the ejection unit 13. Furthermore, widening the common supply channel 18 and common collection channel 19 along the X direction increases the distance between colors. This may reduce printing efficiency.

[0147] Therefore, the cross-section is shown in Figure 15A and Figure 15B In this embodiment, each common supply channel 18 and each common collection channel 19 has the following configuration: each common supply channel 18 and each common collection channel 19 extends along the Y direction and also along the Z direction, which is perpendicular to the X direction, which is the main scanning direction. With this configuration, the common supply channel 18 and the common collection channel 19 can be given a small channel width in the main scanning direction. By giving the common supply channel 18 and the common collection channel 19 a small channel width in the main scanning direction, the ink acting on it during the main scan and along the direction opposite to the main scanning direction (…) Figure 15A and Figure 15BThe oscillating motion of ink within the common supply channel 18 and common collection channel 19 caused by the inertial force applied (as indicated by the bold black arrow in the image) is reduced. This decreases the impact of the ink oscillation on ink ejection. Furthermore, by extending the common supply channel 18 and common collection channel 19 along the Z-direction, their cross-sectional area is increased. This reduces the channel pressure drop.

[0148] As described above, each common supply channel 18 and each common collection channel 19 is given a small channel width in the main scanning direction. This configuration reduces the oscillating motion of ink within the common supply channel 18 and common collection channel 19 during the main scan, but does not eliminate the oscillating motion. Therefore, in this embodiment, in order to reduce the jetting differences between ink types that may be caused by the reduced oscillating motion, the common supply channel 18 and common collection channel 19 are arranged at positions where they overlap each other in the X direction.

[0149] As described above, in this embodiment, the supply connection channel 323 and the collection connection channel 324 are configured to correspond to the ejection port 13. Furthermore, the correspondence between the supply connection channel 323 and the collection connection channel 324 is established such that the supply connection channel 323 and the collection connection channel 324 form an array with the ejection port 13 located between them in the X direction. Therefore, if the common supply channel 18 and the common collection channel 19 have portions that do not overlap with each other in the X direction, the correspondence between the supply connection channel 323 and the collection connection channel 324 in the X direction is disrupted. This miscorrespondence affects the flow of ink in the pressure chamber 12 in the X direction and the ejection of ink. If this miscorrespondence is combined with the effect of the oscillating motion of the ink, there is a possibility that the ejection of ink from each ejection port may be further affected.

[0150] Therefore, by arranging the common supply channel 18 and the common collection channel 19 at a position where they overlap each other along the X direction, the oscillating motion of the ink inside the common supply channel 18 and the common collection channel 19 during the main scan is approximately the same as at any position in the Y direction where the jet nozzles 13 are arrayed. Therefore, the pressure difference generated in the pressure chamber 12 between the common supply channel 18 side and the common collection channel 19 side does not change significantly. This enables jet stabilization.

[0151] Furthermore, some of the liquid jet heads in which the ink is circulated are configured such that the channel for supplying ink to the liquid jet head and the channel for collecting ink are the same channel. However, in this embodiment, the common supply channel 18 and the common collection channel 19 are different channels. Additionally, the supply connection channel 323 communicates with the pressure chamber 12, the pressure chamber 12 communicates with the collection connection channel 324, and ink is ejected from the jet nozzle 13 in the pressure chamber 12. That is, the pressure chamber 12, which forms the path connecting the supply connection channel 323 and the collection connection channel 324, includes the jet nozzle 13. Therefore, in each pressure chamber 12, an ink flow occurs from the supply connection channel 323 side to the collection connection channel 324 side, and the ink inside the pressure chamber 12 is efficiently circulated. The ink inside the pressure chamber, which tends to be affected by the evaporation of ink from the jet nozzle 13, is kept fresh by the efficient circulation of ink inside the pressure chamber 12.

[0152] Furthermore, since two channels, namely the common supply channel 18 and the common collection channel 19, are connected to the pressure chamber 12, ink can be supplied from both channels when high-flow-rate injection is required. That is, compared to a structure that forms only a single channel for ink supply and collection, the structure in this embodiment has the advantage of not only being able to perform efficient circulation but also being able to handle high-flow-rate injection.

[0153] Incidentally, when the common supply channel 18 and the common collection channel 19 are arranged close to each other along the X direction, the oscillating motion of the ink has less impact. The common supply channel 18 and the common collection channel 19 are preferably arranged such that the gap between the channels is 75 μm to 100 μm.

[0154] Figure 17 This is a diagram showing the jetting element substrate 340 as a comparative example. Note that in Figure 17 The supply connection channel 323 and the collection connection channel 324 are not shown in the diagram. Ink that has already received heat energy from the jetting element 15 in the pressure chamber 12 flows into the common collection channel 19. Therefore, the temperature of the ink flowing through the common collection channel 19 is higher than the temperature of the ink in the common supply channel 18. Here, in a comparative example, as... Figure 17 As shown in the dotted circle (α), only a common collection channel 19 exists in a portion of the spray element substrate 340 in the X direction. In this case, the temperature in this portion may locally rise, resulting in temperature unevenness within the spray module 300. This temperature unevenness may affect spraying.

[0155] The temperature of the ink flowing through the common supply channel 18 is lower than the temperature of the ink in the common collection channel 19. Therefore, if the common supply channel 18 and the common collection channel 19 are close to each other, the relatively cooler ink in the common supply channel 18 causes a temperature drop in the ink in the common collection channel 19 at the point where the two channels are close together. This suppresses temperature rise. For this reason, it is preferable that the common supply channel 18 and the common collection channel 19 have approximately the same length, exist at a position where they overlap in the X direction, and are close to each other.

[0156] Figure 18A and Figure 18B This diagram illustrates the channel structure of a liquid ejector head 1 for producing cyan (C), magenta (M), and yellow (Y) inks. In the liquid ejector head 1, as... Figure 18A The diagram shows circulation channels configured for each type of ink. A pressure chamber 12 is arranged along the X direction, which is the main scanning direction of the liquid jet head 1. Furthermore, as shown... Figure 18B As shown, a common supply channel 18 and a common collection channel 19 are arranged along the array of nozzles 13. The common supply channel 18 and the common collection channel 19 are arranged to extend in the Y direction with the nozzle array located therebetween.

[0157] <Connection between the main unit and the liquid injection head>

[0158] Figure 19 This is a schematic structural diagram showing more specifically the connection state of the ink cartridge 2 and external pump 21, which are configured as the main unit of the liquid ejection device 50 of this embodiment, to the liquid ejection head 1, and the arrangement of the circulation pump 500, etc. The liquid ejection device 50 of this embodiment has a structure that allows for easy replacement of only the liquid ejection head 1 in the event of a malfunction. Specifically, the liquid ejection device 50 of this embodiment has a liquid connection portion 700 that allows each ink supply pipe 59 connected to each external pump 21 to be easily connected to and disconnected from the liquid ejection head 1. This allows only the liquid ejection head 1 to be easily attached to and removed from the liquid ejection device 50.

[0159] like Figure 19 As shown, each liquid connection 700 has a liquid connector insertion slot 53a protrudingly disposed on the head housing 53 of the liquid ejector head 1, and a cylindrical liquid connector 59a into which the liquid connector insertion slot 53a can be inserted. The liquid connector insertion slot 53a is fluidly connected to an ink supply channel formed in the liquid ejector head 1 and is connected to the first pressure regulating unit 120 via the aforementioned filter 110. The liquid connector 59a is disposed at the end of an ink supply tube 59, which is connected to an external pump 21 that supplies ink from the ink cartridge 2 to the liquid ejector head 1 by pressurization.

[0160] As mentioned above, Figure 19 The liquid injection head 1 shown has a liquid connection portion 700 that facilitates the attachment, removal, and replacement of the liquid injection head 1. However, if the sealing performance between the liquid connector insertion slot 53a and the liquid connector 59a deteriorates, there is a possibility that ink supplied under pressure by the external pump 21 may leak from the liquid connection portion 700. If the leaked ink adheres to the circulation pump 500, etc., it may cause a malfunction in the electrical system. To solve this problem, in this embodiment, the circulation pump, etc., is arranged as follows.

[0161] Arrangement of circulating pumps, etc.

[0162] In this embodiment, as Figure 19 As shown, to prevent ink leaking from the liquid connection 700 from adhering to the circulation pump 500, the circulation pump 500 is arranged higher than the liquid connection 700 in the direction of gravity. Specifically, the circulation pump 500 is arranged higher than the liquid connector insertion slot 53a, which serves as the liquid inlet in the liquid jet head 1, in the direction of gravity. Furthermore, the circulation pump 500 is arranged at a position that does not contact the constituent components of the liquid connection 700. In this way, even if ink leaks from the liquid connection 700, the ink flows in the horizontal direction, which is the operating direction of the liquid connector 59a, or downwards in the direction of gravity. This prevents ink from reaching the circulation pump 500, which is located higher in the direction of gravity. Furthermore, arranging the circulation pump 500 separately from the liquid connection 700 reduces the possibility of ink reaching the circulation pump 500 through the components.

[0163] Furthermore, the electrical connection portion 515, which electrically connects the circulation pump 500 to the electrical contact substrate 6 via a flexible wiring member 514, is configured to be higher than the liquid connection portion 700 in the direction of gravity. Therefore, concerns about electrical malfunctions caused by ink leakage from the liquid connection portion 700 can be reduced.

[0164] Furthermore, in this embodiment, a wall portion 53b is provided for the head housing 53. Therefore, even if ink is ejected from the opening 59b of the liquid connection portion 70, the wall portion 53b will block the ink, thus reducing concerns about the ink reaching the circulation pump 500 or the electrical connection portion 515.

[0165] The features of this disclosure will be described below.

[0166] (First Embodiment)

[0167] <Circulation channel in the injection module>

[0168] The features of this disclosure will be described below. Figure 20AThis is a partially enlarged view of the spray module 300 according to this embodiment, and is a schematic diagram when viewed along the spray direction. Figure 20B This is a schematic cross-sectional view of the jetting module 300 according to this embodiment. The jetting module 300 of this embodiment has a structure in which a nozzle plate 1006 forming a jet orifice 13, a separate channel layer 1007 mainly forming separate channels, a first substrate 1008, and a second substrate 1009 are laminated in this order along the Z-direction. The structure of the jetting module 300 and the flow of ink in the circulation channels will be described below. Note that... Figure 20A and Figure 20B The arrows in the diagram indicate the direction of ink flow.

[0169] The nozzle plate 1006 has a plurality of ejection ports 13 formed therein for ejecting ink. The individual channel layer 1007 is provided with a plurality of individual channels 1002, a plurality of pressure chambers 12, and a plurality of filters 1003 disposed on the ink supply side and the ink collection side. The first substrate 1008, serving as an element substrate, is provided with an ejection element 15 for ejecting ink, a liquid transport element 1001 for circulating ink, a temperature regulating mechanism 1016 for heating the ink before ejection, a supply connection channel 323, and a collection connection channel 324. In the second substrate 1009, serving as a common channel substrate, a common supply channel 18 communicating with the supply connection channel 323 and a common collection channel 19 communicating with the collection connection channel 324 are formed. The temperature regulating mechanism 1016 is a mechanism for adjusting the ink in the individual channels 1002 to an appropriate temperature (viscosity).

[0170] Multiple individual channels 1002 are formed by a nozzle plate 1006, an individual channel layer 1007, and a first substrate 1008, and are configured to extend along the X direction. Each individual channel 1002 includes an individual supply channel 1004 on the ink supply side and an individual collection channel 1005 on the ink collection side. The individual supply channel 1004 communicates with a supply connection channel 323. The individual collection channel 1005 communicates with a collection connection channel 324. This allows the individual channels 1002 to function as paths through which ink can be supplied and circulated.

[0171] The pressure chamber 12 is a region used to generate energy for jetting liquid, and does not need to be a clearly defined chamber. The jetting element 15 is disposed inside the pressure chamber 12.

[0172] A filter 1003 is disposed between the supply connection channel 323 and the separate supply channel 1004. The filter 1003 is also disposed between the separate collection channel 1005 and the collection connection channel 324. This prevents foreign objects, air bubbles, etc., from entering the separate channel 1002.

[0173] The ejection element 15 is disposed in a separate channel 1002 at a position facing the ejection port 13. The ejection element 15 generates ejection energy for ejecting ink from the ejection port 13. As described above, in this embodiment, an electrothermal conversion element (heater) is used as the ejection element 15, but a piezoelectric actuator (piezoelectric element) may also be used.

[0174] Liquid transport elements 1001 are arranged at predetermined distances in the X direction from the jetting element 15 on the side of the individual supply channel 1004. The liquid transport elements 1001 generate thermal energy for circulating ink in the individual channel 1002. When the liquid transport elements 1001 are driven, the ink is heated and transported by the boiling of the ink film. In this embodiment, an electrothermal conversion element (heater) is used as the liquid transport element 1001, but a piezoelectric actuator (piezoelectric element) may also be used. In this disclosure, the circulation of ink transported by the liquid transport elements 1001 is referred to as microcirculation 1011. This allows ink in the individual channel 1002 to be transported from the individual supply channel 1004 via the pressure chamber 12 to the individual collection channel 1005. The liquid transport elements 1001 can transport liquid even when the liquid jetting device 50 is stopped.

[0175] Ink supplied from the circulation unit 54 flows through the common supply channel 18 and via the supply connection channel 323 into the individual channel 1002 and the pressure chamber 12. Ink that has flowed into the pressure chamber 12 flows out of the common collection channel 19 through the collection connection channel 324. At this time, the circulation of ink transported to the jet module 300 by the circulation unit 54 is referred to in this embodiment as macro circulation 1012.

[0176] Here, the flow resistance between the liquid transport element 1001 and the individual supply channel 1004 is R1, while the flow resistance between the liquid transport element 1001 and the individual collection channel 1005 is R2. Since the liquid transport element 1001 is closer to the individual supply channel 1004 than the individual collection channel 1005, the flow resistance R1 is less than the flow resistance R2. For this reason, the bubbles generated by driving the liquid transport element 1001 tend to grow on the individual supply channel 1004 side. As the bubbles contract, ink flows in to compensate for the volume. Therefore, more ink flows out from the individual supply channel 1004 than from the individual collection channel 1005. As a result, ink flows from the individual supply channel 1004 to the individual collection channel 1005. That is, a microcirculation 1011 is generated. The ratio of flow resistance R1 to flow resistance R2 affects the left-right ratio of the bubbles, which in turn affects the size of the microcirculation flow. In this embodiment, the flow pressure ratio R1 / R2 is preferably set in the range of 0.05 to 0.4. By setting the flow pressure ratio R1 / R2 within this range, the circulating flow within the individual channel 1002 can be maintained within an appropriate range.

[0177] As described above, in this embodiment, the piezoelectric diaphragm pump is used as a circulation pump 500 capable of transporting liquid in the circulation unit 54. The piezoelectric diaphragm pump can be driven on demand only when circulation is required. The timing for driving the piezoelectric diaphragm pump is preferably immediately before driving the injection element 15 and the liquid transport element 1001, or after a long period of inactivity of the injection element 15 and the liquid transport element 1001.

[0178] In this way, in the configuration of this embodiment, when ink is consumed, new ink can be supplied to the individual channel 1002. Moreover, even when ink is not consumed, new ink can circulate in the individual channel 1002.

[0179] <Drive signals for liquid transport components>

[0180] Figure 21 This is a diagram illustrating the injection pulses used to drive the injection element and the drive pulses for the liquid delivery element. When the head driver 1A (see...) Figure 1B When an ejection pulse 1020 is applied to the ejection element 15, ink is ejected from the ejection port 13, and an ejection pulse pause time 1021 occurs until the next ejection pulse 1020 is applied to the ejection element 15. If the head driver 1A applies a liquid transport element drive pulse 1022 to the liquid transport element 1001 during the ejection pulse pause time 1021, the liquid transport element 1001 is driven to generate a microcirculation 1011 in a separate channel 1002. In this embodiment, a liquid transport element drive pulse pause time 1023 is configured between the ejection pulse 1020 and the liquid transport element drive pulse 1022, and between the liquid transport element drive pulse 1022 and the next liquid transport element drive pulse 1022. After the liquid transport element drive pulse pause time 1023 has elapsed, the liquid transport element drive pulse 1022 is applied to the liquid transport element 1001. In this embodiment, during the jet pulse pause time 1021, the liquid delivery element drive pulse pause time 1023 and the liquid delivery element drive pulse 1022 are repeated three times. In this way, by intermittently applying the liquid delivery element drive pulse 1022, the liquid in the individual channel 1002 is intermittently delivered. Thereafter, the head driver 1A (see...) Figure 1B A jet pulse 1020 is applied to the jet element 15, and ink is delivered from the jet nozzle 13. Note that in this embodiment, during the jet pulse pause time 1021, the liquid transport element drive pulse pause time 1023 and the liquid transport element drive pulse 1022 are repeated three times. However, this embodiment is not limited to this example. Preferably, the liquid transport element drive pulse 1022 is applied to the liquid transport element 1001 at least once between the jet pulse 1020 being applied to the jet element 15.

[0181] <Control of the Loop Unit>

[0182] Refer again Figure 6 The macroscopic circulation 1012 in this embodiment is achieved by driving the circulation pump 500 to circulate ink between the jetting module 300 and the circulation unit 54. At this time, based on the CPU 103 (see...) Figure 1B The conditions for driving the circulation pump 500 are determined to drive it on demand. In this disclosure, "driving on demand" means that the circulation pump is not driven stably during printing operations or non-printing operations, and the CPU determines whether to drive the circulation pump based on conditions other than whether there is a printing operation.

[0183] For example, the circulation pump 500 can be started immediately before the printing operation and after a predetermined time period has elapsed since the printing operation was completed. Additionally, if the liquid jetting device has not been used for an extended period, the circulation pump 500 can be periodically activated to reduce the deposition of sediment. Furthermore, sensors for detecting the diffusion state of the color material can be installed in the circulation channel for each color, and the circulation pump 500 can be activated when the concentration of the color material exceeds a predetermined value.

[0184] Even during printing operations, the circulation pump 500 can be temporarily stopped or the drive cycle can be changed to reduce excessive flow in the individual channel 1002. For example, in the liquid jet head 1 of this embodiment, a temperature regulation structure 1016 is used for so-called temperature regulation control to adjust the ink temperature (viscosity) in order to achieve proper jetting. In cases where macroscopic circulation causes more ink to flow in the individual channel 1002 than required and reduces the effect of temperature regulation control, it is preferable to temporarily stop the circulation pump 500 or change the drive cycle. According to the ROM 101 (see...) Figure 1B The program in ) is controlled by CPU103.

[0185] In this manner, according to this embodiment, the circulation unit 54 and the liquid delivery element 1001 are driven independently of each other at the required timing. This allows for micro-circulation 1011 to be generated in a separate channel 1002, while allowing high-flow-rate circulation between the jet module 300 and the circulation unit 54 only at the required timing. This makes it possible to properly suppress ink concentration and deposition throughout the liquid jet head, while suppressing the evaporation rate of ink evaporating from the jet nozzle 13. Additionally, power consumption can be reduced by driving the circulation pump 500 at the required timing.

[0186] Note that in a configuration where macroscopic circulation is always generated, as in Reference 1, even if the temperature of the ink in the pressure chamber is adjusted, cold ink flows into the pressure chamber through circulation. This generates a large amount of waste heat. Therefore, there is a problem that temperature regulation consumes too much electricity. Moreover, because temperature regulation is time-consuming, the start-up of the device until the jetting operation can begin is delayed. In addition, in the configuration of Reference 1, evaporation from the jet nozzle is always advancing, causing a problem of concentration advancement throughout the supply system. Furthermore, there is a problem of increased power consumption in the main body due to the constant driving of the circulation pump. To solve these problems, it is desirable to drive macroscopic circulation at the required time intervals, as in the configuration of this embodiment.

[0187] In this embodiment, in addition to macroscopic circulation using the liquid delivery element 1001, macroscopic circulation is also performed to circulate the ink inside the head using the circulation unit 54, thereby eliminating ink concentration inside the pressure chamber 12. Highly responsive macroscopic circulation is achieved by using a piezoelectric circulation pump 500 and employing a configuration where the circulation path has a short path length completed inside the liquid ejector head. This allows the circulation pump 500 to be driven on demand and suppresses waste heat inside the pressure chamber and evaporation from the ejector nozzle.

[0188] The effects of driving micro-circulation and macro-circulation will be described in three parts below. When micro-circulation is stopped and only macro-circulation is operated, ink concentration and deposition throughout the supply system can be eliminated, while evaporation from the nozzle 13 is suppressed. When micro-circulation is operated and macro-circulation is stopped, circulation can occur only within the pressure chamber 12. Therefore, by driving the liquid transport element 1001 immediately before the ejection operation, the ink inside the channel can be replaced with fresh ink, and the reduction in ejection efficiency can be suppressed. When both micro-circulation and macro-circulation are operated, such as immediately after a long pause in the ejection operation, if the ink is significantly concentrated or deposited in both the supply system and the nozzle, both circulation systems are temporarily driven. This allows ink to circulate throughout the ink channel throughout the head while suppressing waste heat. In this case, macro-circulation allows the ink that has thickened on the ejection unit 15 or the liquid transport element 1001 to flow immediately before ejection. Therefore, the reduction in foaming efficiency caused by the thickened ink on the ejection element 15 or the liquid transport element 1001 can be suppressed.

[0189] (Second Embodiment)

[0190] The loop construction in the second embodiment of this disclosure will be described. Only the differences from the loop construction in the first embodiment will be described.

[0191] <Location path in the injection module>

[0192] Figure 22AThis is a schematic cross-sectional view of the jetting module 300 of this embodiment. The jetting module 300 of this embodiment has a structure in which a nozzle plate 1006 forming a jet orifice 13, a separate channel layer 1007 mainly forming separate channels, a first substrate 1008, a second substrate 1009, and a third substrate 1013 are laminated in this order along the Z-direction. The structure of the jetting module 300 and the flow of ink in the circulation channels will be described below. Note that... Figure 22A The arrows in the diagram indicate the direction of ink flow.

[0193] In the first substrate 1008, an ink ejection element 15 for ink ejection, a liquid transport element 1001 for circulating ink, a supply connection channel 323, and a collection connection channel 324 are formed. In the second substrate 1009, a connection channel 1014 is formed, which communicates with both the plurality of supply connection channels 323 and the plurality of collection connection channels 324, and directly connects a common supply channel 18 and a common collection channel 19. In the third substrate 1013, a common supply channel 18 communicating with the plurality of supply connection channels 323 and a common collection channel 19 communicating with the plurality of collection connection channels 324 are formed.

[0194] In this embodiment, ink flowing from the circulation unit 54 exits through the common supply channel 18, passes through the connecting channel 1014, flows to the common collection channel 19, and then flows back to the circulation unit, creating a macro-circulation 1012. This allows for the suppression of ink concentration and deposition in these channels. Ink flowing from the circulation unit 54 can also flow into individual channels 1002, but in small amounts and without affecting the evaporation rate from the nozzle 13. In individual channels 1002, micro-circulation is generated by the liquid transport element 1001, enabling the suppression of ink concentration in the pressure chamber 12.

[0195] In this embodiment, the macro-circulation 1012 is actively directed toward the connecting channel 1014, rather than toward the individual channel 1002. Therefore, ink evaporation from the ejector 13 can be suppressed. Furthermore, as in the first embodiment, the influence on the individual channel 1002 can be suppressed by generating the macro-circulation 1012 at the required timing.

[0196] In addition to the channel structure mentioned above, such as Figure 22B As shown, a common channel 1014 can be formed by the second substrate 1009 to connect to a plurality of supply connection channels 323 and collection connection channels 324 formed by the first substrate 1008. Moreover, in this case, the configuration enables macroscopic circulation as described above.

[0197] (Third Embodiment)

[0198] The loop construction in the third embodiment of this disclosure will be described. Only the differences from the loop construction in the first and second embodiments will be described.

[0199] <Location path in the injection module>

[0200] Figure 23A This is a partially enlarged view of the jet module 300 of this embodiment when viewed along the jet direction. Figure 23B It is along Figure 23A A cross-sectional view of the section cut by lines XXIIIB-XXIIIB.

[0201] In the nozzle plate 1006, ink ejection orifices 13 are formed near one end and the other end in the X direction. These orifices 13 are arrayed along the Y direction. Two orifice arrays are arranged at positions offset from each other by half a pitch along the Y direction.

[0202] In the individual channel layer 1007, U-shaped individual channels 1002 are formed at positions corresponding to each injection port 13. In addition, in the individual channel layer 1007, a connecting channel 1014 is formed, which is in common communication with the plurality of individual channels 1002 and connects the supply connecting channel 323 and the collection connecting channel 324.

[0203] In the first substrate 1008, jetting elements 15 for generating energy for ink ejection are formed at positions included in each individual U-shaped channel 1002 and facing the ejection nozzle 13. Additionally, in the first substrate 1008, liquid transport elements 1001 for circulating ink in the individual U-shaped channels 1002 are formed at positions included in each individual channel 1002. In this embodiment, the plurality of jetting elements 15 and the plurality of liquid transport elements 1001 are arranged alternately in a row along the Y direction. In the first substrate 1008, a supply connection channel 323 capable of centrally supplying liquid to the plurality of individual channels 1002, and a collection connection channel 324 capable of centrally collecting liquid from the plurality of individual channels 1002 are formed.

[0204] In the second substrate 1009, a common supply channel 18 connected to the supply connection channel 323 and a common collection channel 19 connected to the collection connection channel 324 are formed.

[0205] Each individual channel 1002 is a U-shaped channel formed by the nozzle plate 1006, the individual channel layer 7, and the first substrate 1008. The individual channel 1002 includes an individual supply channel 1004 on the ink supply side and an individual collection channel 1005 on the ink collection side. Such individual channels 1002 are formed near one end and the other end in the X direction.

[0206] In the U-shaped individual channel 1002, the liquid delivery element 1001 is arranged on the side of the individual supply channel 1004 at a predetermined distance from the jetting element 15. In this embodiment, the liquid delivery element 1001 generates thermal energy for circulating ink within the individual channel 1002. When the liquid delivery element 1001 is activated, the ink is heated and transported out through film boiling. This allows for macroscopic circulation 1011 within the individual channel 1002. However, as in the first embodiment, a piezoelectric actuator (piezoelectric element) can be used for both the jetting element 15 and the liquid delivery element 1001.

[0207] According to the configuration of this embodiment, the macro-circulation formed by the circulation unit 54 flows sequentially mainly through the supply connection channel 323, the connection channel 1014, and the collection connection channel 324, and is less likely to enter the U-shaped individual channel. In this way, by minimizing the impact of the macro-circulation 1012 on the U-shaped individual channel, ink evaporation from the ejector 13 can be suppressed. Moreover, as in the first embodiment, by generating the macro-circulation 1012 at the required timing, the impact on the individual channel 1002 can be suppressed.

[0208] (Fourth Embodiment)

[0209] The loop construction of the fourth embodiment of this disclosure will be described. Only the differences from the loop constructions in the first, second, and third embodiments will be described.

[0210] <Location path in the injection module>

[0211] Figure 24A This is a schematic cross-sectional view of the jetting module 300 of this embodiment. The jetting module 300 of this embodiment has a structure in which a nozzle plate 1006 forming a jet orifice 13, a separate channel layer 1007 mainly forming separate channels, a first substrate 1008, a second substrate 1009, and a third substrate 1013 are laminated in this order along the Z-direction. The structure of the jetting module 300 and the flow of ink in the circulation channel will be described below. Note that... Figure 24A The arrows in the diagram indicate the direction of ink flow.

[0212] In the individual channel layer 1007, U-shaped individual channels 1002 are formed at positions corresponding to each injection port 13. Furthermore, in the individual channel layer 1007, connection channels 1014 connecting the supply connection channel 323 and the collection connection channel 324 are respectively formed between the two injection port arrays. In this embodiment, the connection channel 1014 will be referred to as the first connection channel 1014 below.

[0213] In the first substrate 1008, an ink ejection element 15 for ink ejection, a liquid transport element 1001 for circulating ink, a supply connection channel 323, and a collection connection channel 324 are formed in the same manner as in the third embodiment.

[0214] In the second substrate 1009, a second connection channel 1015 is formed that directly connects the common supply channel 18 and the common collection channel 19. In the third substrate 1013, a common supply channel 18 that communicates with the supply connection channel 323 and the second connection channel 1015, and a common collection channel 19 that communicates with the collection connection channel 324 and the second connection channel 1015 are formed.

[0215] In this embodiment, the ink flowing out of the circulation unit 54 primarily flows from the common supply channel 18 to the common collection channel 19 via the second connecting channel 1015 and returns to the circulation unit 54, creating a macro-circulation 1012. A portion of the ink flowing out of the circulation unit 54 flows from the common supply channel 18 to the common collection channel 19 via the supply connecting channel 323, the first connecting channel 1014, and the collection connecting channel 324. On the other hand, micro-circulation is generated in the individual channel 1002 by the liquid transport element 1001. This makes it possible to suppress ink concentration and ink deposition in the individual channel 1002.

[0216] Note that the construction can make, for example Figure 24B As shown, only one connection channel is formed through the first substrate. However, Figure 24A The construction in Figure 24B It is preferred because the macroscopic circulation path can easily reach the injection port to form substrate 320.

[0217] Therefore, according to the configuration of this embodiment, ink evaporation can be suppressed by employing a configuration with the macro-circulation 1012 in the individual channel 1002 as small as possible. Moreover, as in the first embodiment, ink evaporation in the individual channel 1002 can be suppressed by generating the macro-circulation 1012 at the required timing.

[0218] (Fifth Embodiment)

[0219] The loop construction in the fifth embodiment of this disclosure will be described. Only the differences from the loop constructions in the first to fourth embodiments will be described.

[0220] <Location path in the injection module>

[0221] Figure 25A This is a partially enlarged view of the jet module 300 of this embodiment when viewed along the jet direction. Figure 25B It is along Figure 25A A cross-sectional view of line XXVB-XXVB in the middle. Figure 25C yes Figure 25AA magnified view of a portion of the image.

[0222] The jetting module 300 of this embodiment has a structure in which a jetting nozzle forming substrate 320 forming a jetting nozzle 13 and a silicon substrate 310 including a jetting element 15 and a liquid transport element 1001 are laminated in this order along the Z direction. The structure of the jetting module 300 and the flow of ink in the circulation channel will be described below. Note that Figure 25A and Figure 25B The arrows in the diagram indicate the direction of ink flow.

[0223] The silicon substrate 310 is provided with a supply trench 1030 for supplying ink to the individual channel 1002. The supply trench 1030 is formed in a tapered shape from the silicon substrate 310 toward the nozzle forming substrate 320. Ink is supplied from the supply trench 1030 to the individual channel 1002.

[0224] The jetting module 300 of this embodiment does not have a common channel for collecting ink flowing out of the multiple individual channels 1002. The ink flowing out of the individual channels 1002 returns to the individual channels 1002 or moves toward the supply trench 1030. On the other hand, a portion of the ink in the supply trench 1030 is recovered by the circulation unit 54. With this configuration, most of the ink flowing out of the circulation unit 54 returns to the circulation unit 54 and is not supplied from the supply trench 1030 to the individual channels 1002. On the other hand, micro-circulation is generated in the individual channels 1002 by the liquid transport element 1001, which makes it possible to suppress ink concentration and ink deposition.

[0225] As described above, by cycling the macroscopic cycle 1012 at the required time, ink concentration and ink deposition can be appropriately suppressed, while ink evaporation can also be suppressed.

[0226] Other embodiments

[0227] Embodiments of this disclosure can also be implemented by a computer that reads and executes computer-executable instructions (e.g., one or more programs) recorded on a storage medium (also more fully referred to as a "non-transitory computer-readable storage medium") to perform the functions of one or more of the above embodiments and / or includes a system or apparatus comprising one or more circuits (e.g., application-specific integrated circuits (ASICs)) for performing the functions of one or more of the above embodiments. Furthermore, embodiments of this disclosure can be implemented using a method by which the computer of the system or apparatus, for example, reads and executes the computer-executable instructions from the storage medium to perform the functions of one or more of the above embodiments and / or controls the one or more circuits to perform the functions of one or more of the above embodiments. The computer may include one or more processors (e.g., central processing unit (CPU), microprocessor unit (MPU)) and may include separate computers or a network of separate processors to read and execute the computer-executable instructions. The computer-executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include one or more of the following: hard disk, random access memory (RAM), read-only memory (ROM), memory of a distributed computing system, optical disc (such as compressed optical disc (CD), digital versatile optical disc (DVD) or Blu-ray disc (BD)™), flash memory device, and memory card.

[0228] Although this disclosure has been described with reference to embodiments, it should be understood that this disclosure is not limited to the disclosed embodiments. The scope of the appended claims should be given the broadest interpretation to cover all such variations and equivalent structures and functions.

Claims

1. A liquid ejection head configured to eject liquid from ejection ports while moving in a predetermined direction, the liquid ejection head comprising: an ejection unit including: an ejection element configured to generate energy for ejecting liquid from the ejection ports; a pressure chamber communicating with the ejection ports; a separate supply passage for supplying liquid to the pressure chamber; a separate collection passage for collecting liquid from the pressure chamber; and a liquid transport element arranged between the separate supply passage and the separate collection passage and configured to transport liquid from the separate supply passage to the separate collection passage; and a circulation unit fluidly connected to the ejection unit and configured to circulate liquid in a common supply passage for collectively supplying liquid to a plurality of the separate supply passages, wherein the circulation unit is driven on demand based on a predetermined condition determination.

2. The liquid ejection head of claim 1, wherein the circulation unit constitutes a path for circulating liquid only within the liquid ejection head.

3. The liquid ejection head of claim 1, wherein the circulation unit has a pump for circulating liquid.

4. The liquid ejection head of claim 3, wherein the pump is a piezoelectric diaphragm pump.

5. The liquid ejection head of claim 1, wherein the separate supply passage, the liquid transport element, the pressure chamber, and the separate collection passage are arranged in a row along the predetermined direction.

6. The liquid ejection head of claim 1, wherein the separate supply passage, the liquid transport element, the pressure chamber, and the separate collection passage are arranged in a U-shape.

7. The liquid ejection head of claim 1, wherein the circulation unit circulates liquid by transporting liquid in a common collection passage for collectively collecting liquid from a plurality of the separate collection passages to the common supply passage.

8. The liquid ejection head according to claim 7, further comprising: a connection passage connecting the common supply passage with the common collection passage without passing through the pressure chamber, wherein the circulation unit includes a passage for transporting liquid sequentially through the common supply passage, the connection passage, and the common collection passage.

9. The liquid ejection head according to claim 1, further comprising: a temperature adjustment mechanism for adjusting the temperature of liquid in the vicinity of the pressure chamber.

10. The liquid ejection head of claim 1, wherein the liquid transport element is intermittently driven to generate intermittent flow of liquid from the separate supply passage to the separate collection passage.

11. The liquid ejection head according to claim 1, wherein the ejection unit has a configuration in which a nozzle plate, a separate passage layer, an element substrate, and a common passage substrate are laminated, the nozzle plate has the ejection ports formed therein, the pressure chamber, the separate supply passage, and the separate collection passage are formed in the separate passage layer, the ejection element and the liquid transport element are arranged in the element substrate, and the common supply passage is formed in the common passage substrate.

12. The liquid ejection head of claim 11, wherein, the common passage substrate has a common collection passage formed therein for collectively collecting liquid from a plurality of the separate collection passages.

13. The liquid ejection head according to claim 12, wherein A second common channel substrate is laminated between the element substrate and the common channel substrate, the second common channel substrate having a connection channel formed therein for connecting the common supply channel and the common collection channel without passing through the pressure chamber.

14. The liquid ejection head of claim 11, wherein, The liquid-carrying element is an electrothermal conversion element.

15. The liquid ejection head of claim 11, wherein, The liquid-carrying element is a piezoelectric actuator.

16. A liquid ejection apparatus comprising: a scanning unit configured to scan a carriage in a predetermined direction, the liquid ejection head according to claim 1 is mounted on the carriage; a conveying unit configured to convey a sheet in a direction intersecting the predetermined direction, on which sheet droplets ejected by the liquid ejection head are applied; and a control unit configured to control the ejection scanning unit, the conveying unit, the circulating unit, the ejection element, and the liquid-carrying element.

17. The liquid ejection apparatus according to claim 16, further comprising: a printing unit having a program to be executed by the control unit stored therein, wherein the control unit makes a predetermined condition determination according to the program, and drives the circulating unit based on the determination result.

18. A method for controlling a liquid ejection head configured to eject liquid from an ejection port while moving in a predetermined direction, the liquid ejection head comprising: an ejection unit including: an ejection element configured to generate energy for ejecting liquid from the ejection port; a pressure chamber communicating with the ejection port; an individual supply channel for supplying liquid to the pressure chamber; an individual collection channel for collecting liquid from the pressure chamber; and a liquid-carrying element disposed between the individual supply channel and the individual collection channel, and configured to carry liquid from the individual supply channel to the individual collection channel; and a circulating unit configured to circulate liquid in a common supply channel for collectively supplying liquid to a plurality of the individual supply channels, the method comprising: driving the circulating unit as needed based on a predetermined condition determination.

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